[Qt-creator] Qt4ProjectManager plugin renamed to QmakeProjectManager

[Poenitz Andre]

This is just a heads-up for people building from source: 

The Qt4ProjectManager plugin just has been renamed to 
QmakeProjectManager. 

The old name has been "wrong" for quite a while, as the 
plugin handles both Qt 4 and Qt 5 and in the light of the
upcoming promise of interface stability it seemed better
to get the naming right for the Creator 3.0 release.

The change should be mostly invisible to most users
(of course, About->Plugins looks slightly different), but
if you build directly from source you'll need to remove
lib/qtcreator/plugins/QtProject/Q4ProjectManager.pluginspec
and libQmakeProjectManager.so (or your platform's
equivalent to that) manually. 

A clean rebuild would do the trick, too.

I am sorry for the inconvenience this may cause.

Andre'