Added Sources model + controller

commands:
rails generate redmine_plugin_model body_tracking source
project:references name:string description:text
rails generate redmine_plugin_controller body_tracking sources index
create destroy

app/views/sources/create.html.erb

@@ -0,0 +1 @@
+<h2>SourcesController#create</h2>

app/views/sources/destroy.html.erb

@@ -0,0 +1 @@
+<h2>SourcesController#destroy</h2>

app/views/sources/index.html.erb

@@ -0,0 +1 @@
+<h2>SourcesController#index</h2>