PathChooser: Grant direct access to lineEdit's history key

Change-Id: I889b5cd0dbc27144253a9c82567eee59554725a3
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
DebuggerDialogs: Remember debugger path history

Change-Id: I02e6b7ff5e2280cabb0f23de942941756f7bf3a0
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>