Temporary branch for making the cdo tests from the directory "test" running with "make check" and "make distcheck"

This should be possible to run from VPATH build, too

* stdatm creates vertical single gridpoint values for pressure and temperature for a given list of zlevels
* intlevel3d interpolates 3d variables from/to 3d vertical coordinates like height fields

Add libtool support for linking cdo (refs #82)
Make use of CDI's m4 library for configure options
Use Json file for saving/representing configuration status (refs #371)

closes #228

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