Removed deprecated method
Added missing else branch
Removing deprecated warning
WIP image search build/save
Fix SIGILL

Actually only using DescriptorsType& causes error.
Later, when optimizing the code we should remove redundant/unused
attributes and use references/pointers whenever possible.
WIP image search test
Added documentation to ImageSearch class
Disabled test_imsearch

test_imsearch is actually an integration test and should be executed at
a later stage, not for unit testing.