Doc: Polish creating plugins
Doc: Polish creating plugins

Change-Id: If0692c978e566797391b1a553a76343e605cd2b8
Reviewed-by: Leena Miettinen <885fda02d52616fec24ed5fed9b3f0568fce3ead@theqtcompany.com>

martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator