QtVersionManager: Emit less signals
QtVersionManager: Emit less signals

Emit less signals when reading the qtversions.xml file provided
by the SDK. Especially do not claim a Qt version was removed and
added again on updates. This could potentially cause BuildConfigs
to update themselves in stupid ways.

Change-Id: I5e2b3ac4725f4a30910520e57ca0bbf9fe595f7f
Reviewed-by: Daniel Teske <d8a411aec9a206efedb4d45b75fe8d13f1e2b628@nokia.com>

malikcjm/qtcreator,farseerri/git_code,danimo/qt-creator,syntheticpp/qt-creator,martyone/sailfish-qtcreator,KDE/android-qt-creator,kuba1/qtcreator,danimo/qt-creator,maui-packages/qt-creator,kuba1/qtcreator,syntheticpp/qt-creator,xianian/qt-creator,Distrotech/qtcreator,Distrotech/qtcreator,omniacreator/qtcreator,malikcjm/qtcreator,syntheticpp/qt-creator,martyone/sailfish-qtcreator,kuba1/qtcreator,richardmg/qtcreator,maui-packages/qt-creator,darksylinc/qt-creator,maui-packages/qt-creator,malikcjm/qtcreator,malikcjm/qtcreator,syntheticpp/qt-creator,KDE/android-qt-creator,maui-packages/qt-creator,amyvmiwei/qt-creator,omniacreator/qtcreator,danimo/qt-creator,richardmg/qtcreator,martyone/sailfish-qtcreator,duythanhphan/qt-creator,colede/qtcreator,syntheticpp/qt-creator,richardmg/qtcreator,richardmg/qtcreator,danimo/qt-creator,amyvmiwei/qt-creator,darksylinc/qt-creator,KDE/android-qt-creator,xianian/qt-creator,amyvmiwei/qt-creator,maui-packages/qt-creator,malikcjm/qtcreator,maui-packages/qt-creator,martyone/sailfish-qtcreator,danimo/qt-creator,danimo/qt-creator,kuba1/qtcreator,darksylinc/qt-creator,xianian/qt-creator,duythanhphan/qt-creator,amyvmiwei/qt-creator,kuba1/qtcreator,amyvmiwei/qt-creator,amyvmiwei/qt-creator,richardmg/qtcreator,martyone/sailfish-qtcreator,colede/qtcreator,kuba1/qtcreator,colede/qtcreator,colede/qtcreator,duythanhphan/qt-creator,xianian/qt-creator,farseerri/git_code,darksylinc/qt-creator,martyone/sailfish-qtcreator,Distrotech/qtcreator,xianian/qt-creator,farseerri/git_code,duythanhphan/qt-creator,richardmg/qtcreator,colede/qtcreator,xianian/qt-creator,danimo/qt-creator,KDE/android-qt-creator,farseerri/git_code,xianian/qt-creator,duythanhphan/qt-creator,AltarBeastiful/qt-creator,darksylinc/qt-creator,omniacreator/qtcreator,KDE/android-qt-creator,kuba1/qtcreator,colede/qtcreator,martyone/sailfish-qtcreator,kuba1/qtcreator,malikcjm/qtcreator,kuba1/qtcreator,syntheticpp/qt-creator,farseerri/git_code,martyone/sailfish-qtcreator,KDE/android-qt-creator,farseerri/git_code,duythanhphan/qt-creator,colede/qtcreator,omniacreator/qtcreator,farseerri/git_code,AltarBeastiful/qt-creator,Distrotech/qtcreator,syntheticpp/qt-creator,martyone/sailfish-qtcreator,danimo/qt-creator,darksylinc/qt-creator,AltarBeastiful/qt-creator,amyvmiwei/qt-creator,duythanhphan/qt-creator,Distrotech/qtcreator,darksylinc/qt-creator,xianian/qt-creator,AltarBeastiful/qt-creator,AltarBeastiful/qt-creator,AltarBeastiful/qt-creator,KDE/android-qt-creator,richardmg/qtcreator,AltarBeastiful/qt-creator,omniacreator/qtcreator,omniacreator/qtcreator,maui-packages/qt-creator,Distrotech/qtcreator,darksylinc/qt-creator,KDE/android-qt-creator,farseerri/git_code,AltarBeastiful/qt-creator,danimo/qt-creator,amyvmiwei/qt-creator,malikcjm/qtcreator,Distrotech/qtcreator,xianian/qt-creator,omniacreator/qtcreator