Rework "regexp" in listUsersPaginated / getUsersCount in class.sqlAuthDriver.php
Now "^a" matches everything that start with a
"a$" matches everything that end with a
"^a$" matches exactly a (wasn't working)
"a" matches everything that contains a (was matching exactly a)

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@fiducial.net>