added:  debian packaging control files

Next round.

This adds (not yet 100% done) debian packaging for the release branch, based on the CMake build system.

for any bikeshedders:

shall we name the packages libopmfoo or libopm-foo (in this case foo=core).
currently, i have it as libopmcore, but this is easy to change.

for @rolk i guess;
1) the .la file is not installed
2) what's the idea with the .so.debug?
3) is it intentional that make install-html generates the pdf doxy? this means we need to depend on the latex packages severely increasing the pbuilder build time.
4) we have some noise issues in /usr/share/doc. we'll get one dir for the package name with the packaging copyright etc (e.g. /usr/share/doc/libopmcore1) then we get another with the doxy (/usr/share/doc/opm-core). how to resolve, or shall i just ignore.