Layout Locations and Chooser updates

- Added support for the following layout attributes: libraryset
(replaces the old location name), numbuttons, numencoders, panelwidth,
panelheight, numparameters and excludefromchooser.
- Removed location name from Layout Locations window (replaced by the
libraryset in layout xml)
- Replaced Reset button in Layout Locations with a Rebuild Library
button.
- Tweaked the UI of the Layout Chooser