Remove AutoTools files that searches for libraries

These are now superceded by CMake equivalents, and will over time
diverge from the main tree as they are no longer maintained.
Library to pick up configuration from pkg-config files

Pkg-config files are written as part of the CMake configuration, and
these can be imported into AutoTools-driven projects to get the correct
compiler and linker options that has been probed.
Compatibility module for dunecontrol-driven clients

If a client generated with duneproject/built with dunecontrol has a
dependency to opm-core, the macros defined in this file is expected
to exist and will be called to search for the opm-core library.

All that is done here is to use the pkg-config helper module and
import the configuration that was written by the CMake system (which
even may have been called earlier in the same dunecontrol "session")
Merge pull request #248 from rolk/248_m4

Replace remnants of original autotools config with m4 that imports the CMake config