FEATURE: multi-column sorting on task and document lists added.
IMPROVEMENT: multi-column sorting made configurable, in stead of just configuring 1 default sorted column.
BUGFIX: removed double definenition of aaSorting in tasks datatable.
IMPROVEMENT: renamed document datatable from 'tasks' to 'documents'.
IMPROVEMENT: removed bState attribute from documents datatable, it made all document datatables interfere with each other.