Added auto format on save in route editor

Added an executionEventListener that listens to events, checks the event is a save event, checks that the event originated from the correct route editor instance, checks that the auto format route formatter preference is enabled, and then, if all checks are as expected, formats the route file.

Corresponding preference field was added to the Route Editor's formatter preference page.

Fix #117
Code completion on a route editor's action now works on a single word.

The problem lied in the MembersLocator subclasses; when creating a MembersComputer they did not handle the case when the prefix was the EmptyPackage. The fix was to handle that case and return the appropriate MembersComputer whose allMembers field was overridden to be the declarations found in the RootClass in addition to the declarations of the prefix itself (i.e. the EmptyPackage).

It should be noted that completion does not work on members of modules or classes found in the default package. However, this should be a separate issue ticket, and should be investigated further to see if play supports action methods coming from these sources before implementing a fix.

Fix #126
Merge pull request #142 from jhaberstro/route-editor-autoformat-on-save-#117

Added auto format on save in route editor
Merge pull request #135 from jhaberstro/route-editor-single-word-completion-#126

Code completion on a route editor's action now works on a single word.