core-4559 fix app enabling issue in belphegor
CORE-4383 Updates to AppsView and Presenter for Drag-n-Drop support.

Updated AppsViewImpl#tree and grid to protected so that Belphegor has access to them for Drag-n-Drop support.
Added getAppGroupFromElement and getAppFromElement methods to AppsView and AppsView#Presenter, required for Drag-n-Drop support.
CORE-4383 Updates to allow Groups to reload in Belphegor.

Changed AppsViewPresenter#initHandlers to protected, so Belphegor can initialize its group refresh handler there.
Added an AppsViewPresenter#reloadAppGroups method so that groups can be refreshed, and added a 'loading' mask during group loading.
Added an AppsView#clearAppGroups method for the new reloadAppGroups method.
CORE-4584 Remove Singleton AppGroupTreeStoreProvider.

Updated AppsGinModule to no longer use a Singleton AppGroup TreeStore.
Using a Singleton store caused the AppGroup Tree in the ui-pipelines-module to throw exceptions when AppsView#updateAppGroup was called from the main Apps window (such as when updating AppGroup counts).
Removed the AppGroup TreeStore parameter from AppsViewImpl, otherwise it would reference a separate store that its Tree was not using.
Updated AppsViewPresenter#go(HasOneWidget) to call go(HasOneWidget, HasId, HasId), since the categories will no longer be automatically loaded in a Singleton TreeStore for ui-pipelines-module by the Apps window's go(HasOneWidget, HasId, HasId) call.
Merge branch 'master' into STABLE