Added SPF record support

- Ported fix for bnc#758769 from YCP to Ruby
Optimized checking newly added / edited records
Requiring "yast" in each test file so they can be called externally
Refactoring StoreSoaTab

- Ops.add was too hard to understand
Unified quotes
Other way of merge
Added changes file entry and new version
DRYied thanks to Roman's idea
Fixed gettext
Fixed join syntax
More Ruby-like DRYing
Merge pull request #23 from kobliha/master

Fixes and small refactoring