improve documentation for capabilities tag (part of xml description for service)
improve documentation for capabilities tag
(part of xml description for service)

Task-number: QTMOBILITY-337

KDE/android-qt-mobility,tmcguire/qt-mobility,enthought/qt-mobility,kaltsi/qt-mobility,kaltsi/qt-mobility,qtproject/qt-mobility,tmcguire/qt-mobility,tmcguire/qt-mobility,KDE/android-qt-mobility,tmcguire/qt-mobility,kaltsi/qt-mobility,qtproject/qt-mobility,enthought/qt-mobility,qtproject/qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility,qtproject/qt-mobility,enthought/qt-mobility,enthought/qt-mobility,KDE/android-qt-mobility,qtproject/qt-mobility,enthought/qt-mobility,enthought/qt-mobility,kaltsi/qt-mobility,kaltsi/qt-mobility,KDE/android-qt-mobility,tmcguire/qt-mobility