Filter on enrolled users page use role param to perform filtering by role,
and unassign role also contain role param to remove user role in course
which used to conflict. Looking at assign role, we use roleid param, so
using roleid for unassigning as well
At the same time this commit introduces a standardised dialogue YUI module to enrol and implements it across the board.
This commit also addresses MDL-23292 and MDL-23319.
* Set the default per page limit to 100 instead of 20
* Set the default enrolment role to enrol_manual:roleid config
* Added course name to page title
* Fixed centering bug of cohort dialogue
* Fixed double display bug