Don't expose ViMbAdmin's patch level in the footer

[PhrozenByte]

Exposing the exact patch level allows attackers to easily identify likely vulnerable instances of ViMbAdmin if a security flaw happens to be found. This commit simply replaces the exact version string ('3.3.0') with the milestone version string ('3.3') in ViMbAdmin's footer. See 013cfec60b4900c661e1cc75b20d28b6a377f8ee

Additional changes:

• Remove abandoned Google Groups links from footer: If Google Groups or any other kind of forum is revived, one should probably rather add the links to ViMbAdmin's website and the GitHub repo instead, not include it in the footer of every single ViMbAdmin instance.
• Sync footer of 'myskin' template with default footer

[barryo]

Merged with minor change - keeping full version for admins.