[Trunk] Entering "input mode' is now mandatory ? (regression)

I was used to create a score and press C, D, C, D quite quickly to make a test score. I ended up with for quarters and it was great. In the current trunk, it's necessary to press N and enter "input mode" to begin score editing.

Even if "input mode" is necessary in the inner logic of MuseScore, we should try to remove this paradigm in MuseScore user interface.

What do you think?