build: Compose fixes

The live target has the same base_ref as runtime, don't compose installed-tests
if there are no components (previous commit didn't actually fix it).
build: Rebuild already built source snapshot if forced

If one or more components are specified by command line, rebuild them
even if the last source snapshot was already built.
build: Rebuild base if forced

Users can trigger base rebuild.
build: Add runtime components to devel targets

These targets need also the runtime components otherwise the system
won't boot.
Default configure options for all build systems

At the moment we only support arguments for build API compatible
configure scripts via config-opts.

Read default-config-opts instead of config-opts from manifest.
This entry is a dictionary, keys are build system names (buildapi,
qmake and cmake) and values are list of default configure arguments.

Build system will add those arguments to component specific arguments.

Closes #33