Use template data for new templates and fix alias bug

Objectives:

* Use template data for templates added to a transclusion using
  the list controls
* Cache template data between different instances of the dialog
* Allow placeholders to be replaced with templates asynchronously
* Save http request and abort pending requests on close

Also:
* Fix breakage of (unused) method getParameterAliases
  (dont delete aliases)
* Remove unused method getTemplateSpec.

Bug: 49778
Change-Id: I391e51cb900ef5560455d6f3d4d2a8b99ed2b034