tests: Added bindings/cpp to rpath for tests binaries
Cache: Don't always write "cache is not supported"

Add this message to log only if IO_FLAGS_CACHE is passed
tests: Added one more lookup test

For case if file is present not in all groups
tests: Added possibility to build test.cpp withous elliptics sources
Merge pull request #295 from euroelessar/master

Tests improvements
Merge branch 'master' of github.com:reverbrain/elliptics