Bitnamiのインスコ環境は以下
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.

Template plugin installをDLし解凍
c:\bitnami\redmine2.6-1.0\apps\redmine\htdocs\plugins
にフォルダごと置く

まずは一般的なrakeコマンド実施（たぶんUbuntu用）

C:\Bitnami\redmine-2.6.1-0>rake redmine:plugins:migrate RAILS_ENV=production
rake aborted!
No Rakefile found (looking for: rakefile, Rakefile, rakefile.rb, Rakefile.rb)
(See full trace by running task with --trace)

rekeファイルが見つからない？？
ならば

rake動かないようなのでbundle execで実施

C:\Bitnami\redmine-2.6.1-0>bundle exec rake redmine:plugins:migrate RAILS_ENV=production
Could not locate Gemfile or .bundle/ directory

なんだかdirが違うようなので

C:\Bitnami\redmine-2.6.1-0\ruby\bin>bundle exec rake redmine:plugins:migrate RAILS_ENV=production
DL is deprecated, please use Fiddle
Could not locate Gemfile

DLはdeprecated？
Fiddleを使え!
う～、余り遭遇しない単語
deprecateは非難、反対を唱える、たしなめる・・・

ググルと

DL は .dllや.soなどのダイナミックリンクライブラリーを使うためのライブラリーです。これは Ruby の 2.0 から deprecated(非推奨) になりました。
そのため、「DL ではなく、同じ目的のライブラリーである Fiddle の方を使ってください」というメッセージがでています。
これを消すためには、実行されたスクリプト中に DL を使っているところがあるはずなので、そこを Fiddle に書き直す必要があります。
ただ、2.0 でも DL は一応残してあるので、これはエラーというよりもワーニングで、そのままでも使えないことはないと思います。

信じてhtdocsでbundle実行

C:\Bitnami\redmine-2.6.1-0\apps\redmine\htdocs>bundle exec rake redmine:plugins:
migrate RAILS_ENV=production
Warning: this Gemfile contains multiple primary sources. Using source more than once without a block is a security risk, and may result in installing unexpect
ed gems. To resolve this warning, use a block to indicate which gems should come
from the secondary source. To upgrade this warning to an error, run bundle con fig disable_multisource true.
Migrating redmine_issue_templates (Redmine Issue Templates plugin)...
== CreateIssueTemplates: migrating ===========================================
-- create_table(:issue_templates)
-> 0.0624s
-- add_index(:issue_templates, :author_id)
-> 0.0780s
-- add_index(:issue_templates, :project_id)
-> 0.0468s
-- add_index(:issue_templates, :tracker_id)
-> 0.0156s
== CreateIssueTemplates: migrated (0.2340s) ==================================

== CreateIssueTemplateSettings: migrating ====================================
-- create_table(:issue_template_settings)
-> 0.0000s
== CreateIssueTemplateSettings: migrated (0.0156s) ===========================

== AddIssueTitleToIssueTemplates: migrating ==================================
-- add_column(:issue_templates, :issue_title, :string)
-> 0.1248s
== AddIssueTitleToIssueTemplates: migrated (0.1716s) =========================

== AddPositionToIssueTemplates: migrating ====================================
-- add_column(:issue_templates, :position, :integer, {:default=>1})
-> 0.0312s
== AddPositionToIssueTemplates: migrated (0.0468s) ===========================

== AddShouldReplacedToIssueTemplateSettings: migrating =======================
-- add_column(:issue_template_settings, :should_replaced, :boolean, {:default=>f
alse})
-> 0.0312s
== AddShouldReplacedToIssueTemplateSettings: migrated (0.0468s) ==============

== AddIsDefaultToIssueTemplates: migrating ===================================
-- add_column(:issue_templates, :is_default, :boolean, {:default=>false})
-> 0.0312s
== AddIsDefaultToIssueTemplates: migrated (0.0468s) ==========================

== AddEnabledSharingToIssueTemplates: migrating ==============================
-- add_column(:issue_templates, :enabled_sharing, :boolean, {:default=>false})
-> 0.0468s
== AddEnabledSharingToIssueTemplates: migrated (0.0468s) =====================

== AddInheritTemplatesToIssueTemplateSettings: migrating =====================
-- add_column(:issue_template_settings, :inherit_templates, :boolean, {:default=

false, :null=>false})
-> 0.0156s
== AddInheritTemplatesToIssueTemplateSettings: migrated (0.0156s) ============

== CreateGlobalIssueTemplates: migrating =====================================
-- create_table(:global_issue_templates)
-> 0.0312s
-- add_index(:global_issue_templates, :author_id)
-> 0.0312s
-- add_index(:global_issue_templates, :tracker_id)
-> 0.0468s
== CreateGlobalIssueTemplates: migrated (0.1248s) ============================

== CreateGlobalIssueTemplatesProjects: migrating =============================
-- create_table(:global_issue_templates_projects, {:id=>false})
-> 0.0156s
== CreateGlobalIssueTemplatesProjects: migrated (0.0156s) ====================

== RemoveIsDefaultFromGlobalIssueTemplates: migrating ========================
-- remove_column(:global_issue_templates, :is_default)
-> 0.0936s
== RemoveIsDefaultFromGlobalIssueTemplates: migrated (0.1092s) ===============

C:\Bitnami\redmine-2.6.1-0\mysql\bin>
で一応Pluginが通った様子

続いてAvatarのpluginインスコをチャレンジ

Bitnami Redmineでredmine_local_avatars installをやってみた、結果インスコできなかったを記録