moved installation of passenger to docker file
install: cached gems for local bundle install

Basically to speed up development. Cache will be updated at every
redmine upstream update.
moved themes script to themes/install
themes: package all themes
themes: added bash shebang to the install script primarily to trigger syntax highlighing
moved plugins script to plugins/install
plugins: package all plugins
Merge branch 'feature/quick-build'
plugins: install attach by url plugin