check if the account is a guest account

Some attributes of a given account shall not be exported from LDAP even
if set, due to the fact that this account is a guest account. We make
the guestGid configurable, as different projects might have different
gidNumbers for that.

Signed-off-by: Martin Zobel-Helas <zobel@debian.org>
remove superfluous space
Signed-off-by: Martin Zobel-Helas <zobel@debian.org>
Merge pull request #1 from zobelhelas/master

adds is_guest_account() method to User class