-[PANEL] Added a lot of events to make sure layer information is updated properly in all cases.
-[PANEL] Layer names are treated in a special way to make sure they are updated with the layer name every time it's needed
-[PANEL] Much better text change handling. A timer is scheduled and rescheduled to make sure the text is saved as soon as the user stops typing.
-[EXPORTER] Added functions to load default values for unused metadata fields.
-[EXPORTER] The exporter now exports folders as PNGs properly.
-[EXPORTER] The XMP library is only unloaded if it was loaded by the function trying to load it.
-[EXPORTER] The exporter now loads default values for all unused metadata fields in the document and every exported layer.
Merge branch 'master' of github.com:TrompoGames/p2gui.js