add itemChooser plugin
updating default layout and elements

- adapt Common/admin_index
- include choose.js in admin layout
- include chooser field in default search element
change Links/admin_form to use chooser
updating Node chooser implementation

also renames Nodes/admin_links to Nodes/admin_chooser
implement Block chooser
change Attachment/browse to use admin_popup layout
implement User chooser
adding chooser usage example
do not combine add|edit view when $view is a path
remove implicit addition of Paginator

helpers are lazy loaded in 2.3 and skipping implicit addition here
allows plugins to use an alias for Paginator helper
search: update button urls to use 'querystring'
use ^= (starts with selector)
moved JavaScript code out of TinymceHelper. now keeps RTE related code in `Croogo.Wysiwyg`.
the Wysiwyg plugin.
moved fields configuration to Wysiwyg plugin.
dependencies loaded first.

There could be scenarios where Tinymce appears before Wysiwyg in Hook.bootstraps. But Wysiwyg is a dependency plugin of Tinymce. In that case we need to reorder the list of plugins to be loaded.

This could become a part of a lib in the future or done in Extensions plugin whenever a plugin is activated/deactivated.
Updating view fallback mechanism

For plugins that extend NodesController, we should allow fallback to
use views from core Nodes plugin (if none is found in current theme).
adding tests for _viewFallback
Merge remote-tracking branch 'rchavik/1.5-plugin-view-fallback' into 1.5
add $showActions allowing hiding of actionsBlock

to hide 'actions' block:

	$this->set('showActions', false);

in the view.

Fixes #346