Gonzalo Rodriguez Fernandez / gammalib

We should avoid using threads as this has portability issues.

The samp.hub.shutdown request allows a client to shutdown the VO Hub. This is not part of the SAMP protocol but does not harm. It is basically needed for unit testing.

The Hub is searched for when a client is initialised so that one can ping a Hub from a client.

Rename the methods and do some refactoring and clean up of the code.

Conflicts:
	src/vo/GVOClient.cpp
	test/test_GVO.cpp
	test/test_GVO.hpp

The bilinear interpolator class holds indices and weights for bilinear interpolation. It has an interpolation operator that operates on a linear array of double precision values.

The GModel::is_valid() method now allows specifying empty strings for the instrument and id parameters that will skip the specific model validity check. This allows to check for models of a given identifier whatever the instrument, or for models for a given instrument, whatever the identifier.

… GSkymap object. Existing pixel values are kept, any new pixel values will be set to zero. Add an appropriate unit test.