Get rid of the weird old signature:
- int StringType::to_int(bool& ok) const
And replace it with sensible new signature:
- Optional<int> StringType::to_int() const
We also clean up some old references to the old G prefixed GUI classes
This also fixes a potential bug with using: C_OBJECT_ABSTRACT(GAbstractButton)
instead of C_OBJECT_ABSTRACT(AbstractButton)