Case insensitive ldap search, and validators

Issue #78 resolved
Marcin Kuzminski
repo owner created an issue

Well after TkSoh pointed out that ldap should do case insensitive lookups, I thought that this should be implemented in other places of RhodeCode,

This is needed to be fixed:
make ldap do case insensitive searches
make email/user validators check on case insensitive terms.