new customActionLayerTreeCheck()

added customActionLayerTreeCheck() to permit custom actions on check boxes in layer tree
Add customActionLayerTreeCheck

Added new custom function to manage user click on the layerTree (TOC)
Merge pull request #108 from luca76/master

new customActionLayerTreeCheck() for Customizations.js
fix issue with search table change when changing theme
Merge pull request #9 from qgis/master

Merge from main