JBIDE-17979 Content Assist in Angular Expressions in JBoss Tools HTML Editor

Angular Content Assist Computer is enabled in JBoss Tools HTML Editor

Signed-off-by: vrubezhny <vrubezhny@exadel.com>
JBIDE-18034 jst.web.ui test failure
JBIDE-17993 Default ionic js/css references for ionic palette components

Default js/css libraries are registered with an extension point.
Methods are added to IHTMLLibraryVersion that check if a library
is preferred and if it is already referenced by a file.