Fixes for compilation issued in conditions on mac

Thanks to help from @davidlt, here is finally a set of fixes to solve the various compilation issues on Mac OS X (10.8 for now). The basic fix is to move some template instantiations out from the eos headers into a small .cc file and compile this as library (done in CondFormats/Serialization).

As now there is a (small) lib created for CondFormats/Serialization, we needed to add the corresponding use-statements in all BuildFiles of packages storing Conditions.