GUI: fixed filtering of applications by users name

- Fixed case when filtering by whole user's name didn't
  returned any applications, even thou they were
  present in table.
Merge pull request #136 from zlamalp/appfix

GUI: fixed filtering of applications by user's name
Core: attribute U:D:sshPublicKey can be null

Null in value is allowed in the module for U:D:sshPublicKey.

We still don't have something like "optional" attributes for service. So
for this attribute we still need to allow null value in module therefore
the services can mark it as "required" and GEN script must be ready to
get null in this attr.

For services that really reuires not null ssh key, we temporary use
U:D:sshPublicAdminKey attribute.