Update plugins to 2.3

The most significant changes are:

  1. GSLayer.selection does not need any parentheses.
  2. .bezierPath does not need any parentheses anymore, be it of a layer, a path or a component.
  3. GSNode.type does not yield an integer anymore. Compare it to the constants GSLINE, GSCURVE, GSOFFCURVE To remain backwards compatible. To make sure these constants are loaded properly, add this line at the beginning: from GlyphsApp import GSLINE, GSCURVE, GSOFFCURVE.

If you want to remain backwards compatible for points 1 and 2, add a try...except and try with parentheses first, and add the variant without parentheses in the except clause.