[eclipse-pmc] API Addition: Join Lines Editor Action

[Daniel Megert <daniel_megert@xxxxxxxxxx>]

In order to add the ability to join lines in editors I hereby request the
following API additions:
- command and key binding definition to the plugin.xml
- new constants to help, action definition and action id interfaces
- new join lines action


GOALS/BENEFITS:
- new editor action that allows to join lines


CORRESPONDING BUG:
- [api][typing] Add the ability to join lines
      https://bugs.eclipse.org/bugs/show_bug.cgi?id=41573


RISKS:
No known risks.


PERFORMANCE IMPACTS:
- existing code is not affected


Dani