ds 6.x-1.5

- #1293420 by Feng-Shui: Custom build mode key name can exceed db field size.
- #1169466 by grahamgilchrist: do not use block templates if content is empty.
- #1003380 by vadym.kononenko: views field class should be added by default.
- #1004096 by swentel: deleting a build mode breaks synced build modes.
- #1016664 by jstoller: Add field count variable to groups.
- #1059336 by jstoller: Add field variables containing groups and regions.
- #1194922 and 1194914 by swentel and dbeheydt: fix notices with new patch.
- #1221036 by jstoller: fix notice due to function param change in features.
- #1230038 by swentel: fix (public) xss exploit.
- Hide the classes select box on views fields if there are no styles.

- #1168130 by swentel: backport some of the techniques of D7 storage, was included but has been removed. It is available in 6.x-2.x.