Battery and String Checks

Changelog:

• 2.0.0 - migrated to CMK 2.2
• 2.1.0 - migrated to CMK 2.3
• 2.1.2 - typo fix
• 2.1.3 - check_levels for sub values in bacs_string
• 2.2.0 - migrated to CMK 2.3 API
• 2.2.1 - fixed snmp section in bacs battery
• 2.3.0 - fixed old level params