STATIC: <something>--static extends <something> and overrides some parameters to link statically.
Rationale: The default behavior in slapos seems to be dynamic linking, so currently the special case is the static one and it can be reached simply by overriding parameters.

DEP: dep--<something> extends <something> and overrides some parameters to use the host version of the dependencies.
Rationale:
- This is only for development and in particular packaging with OBS. The goal is mainly to be able to bypass the compilation of at least *some* building tools and therefore increase speed up the debugging process dramatically.
- Currently the same buildout files are used in this case, so it is only needed to override some parameters, and therefore it is only needed to extend the already existing <something>.

Note: "dep_" was initially choosen instead of "dep--", but it seems that "_" is forbidden in Debian package name (because "_" is the separator between the package name and its version).