task-x11-server: import from Angstrom

* from meta-angstrom revision 8aa9581a920abae8878df2f3faf9857474edd1f8
* added RPROVIDES to be able to drop server part from task-x11
* updated DESCRIPTION to match
* renamed to task-x11-server for upgradeable path

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>