Improve Copy/CutLine actions usability

This patch implements two features:
1. Reimplement CopyLine to move text cursor at the beginning of line
2. Add copy/cutLine action to Advanced Edit menu, to make it
   discoverable for editor users.

Change-Id: I0bf336ebee4dbf5afd2c759e47b1830271bd9d18
Reviewed-by: David Schulz <david.schulz@digia.com>