Markov Code Fixes

Hi Luigi,
here are some fixes to the Markov model code. The changes are exclusively affecting the files in ql/experimental/models (and the code in the test-suite). I would be grateful if you could merge them already into the 1.3 release.
Thank you
Peter

note: the file test-suite/markovfunctional.cpp shows many irrelevant changes, I believe because some reformatting was done in parallel to my changes. To avoid the merging I just replaced the file with a new version containing spaces instead of tabs. I hope this is how you expect it, otherwise please just tell me.