Improvements on Marsupial

 - Category field added to rcontent activities
 - Fixed bug on checking credentials URL
 - Fixed saving grade items on activities with ForzarGuardar=1
 - Code sorting
 - Fixed version.php on mybooks block
 - Specify error 1016
 - Some improvements on Marsupial configuration style
 - Language changes and some error translations added
 - Open rcontent popup windows throught GET instead of POST