QmlDesigner: Check if the puppet source are newer than puppet

And recompile puppet in that case.

Change-Id: Ia19d54aaa83a4b267de515b6eac5d367f943d7c6
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>
QmlDesigner: Remove call to SubComponentManager::update

It has no model attached so is doing nothing and called later again.

Change-Id: Ide36ba5640ff18e29d5be2ad5911ed448f37c92b
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>