New plugin to read FITS tables.  Note, to compile kst on my machine requ...

...ired

me to remove the KST_THREAD_LOCAL keywords from kst_atof.h and kst_atof.cpp.
This is because my compiler doesn't seem to support "thread local storage",
or whatever that is.

Secondly, I had to disable the fitsimage plugin in
src/datasources/CMakeLists.txt. For some reason, I got errors as if the cfitsio
libraries weren't being loaded properly, even though "#include <fitsio.h>" was
used in fitsimage.h.

Note, my plugin, which also uses fitsio, worked perfectly, so I don't think
it was just a problem with linking.

In this commit, I did not include the changes I made to kst_atof.h,
kst_atof.cpp and the CMakeLists.txt file.