Updated .gitignore.
[[ MeasureText ]] measure the size text needs if drawn with the effective font of the given object
[[ MeasureText ]] added docs, added error if object is not open
[[ MeasureText ]] moved text measurement to MCObject. Possibly useful for the engine elsewhere. Removed object not open error.
[[ MeasureText ]] Made mapfont() / unmapfont() private as external uses can now use measuretext().
[[ MeasureText ]] Updated group's use of mapfont()/unmapfont() to go via measuretext() instead.
Merge branch 'feature-measure_text' into develop