Use MWOAuthUtils::grantName() to fix broken messages

* Made grantName() return a string (as the callers really want) and fixed some
  special pages to escape checkmatrix labels (which HTMLForm does not do itself).
* Added a grantNames() function for convenience.

Change-Id: I934e9ebde513b63ac88ad0aa13a89c41ecfc53ca
Merge "Use MWOAuthUtils::grantName() to fix broken messages"