Add exception raising option

I added a long-needed command-line option to robots that removes the static RAISE_EXCEPTION declaration into a dynamic option.

Thus you can run robots by hand & get a stacktrace, but when run through e.g. cron, they will use the error-reporting.

Also, I added versioneer.py to produce better package names based on tags and intermediate commits. Thus in the future, the versions of a package depend on a tag in git instead of some hard-coded value.

Last but not least the abl.robot.test now is a bit more featureful, mainly it accepts configurations now as single string, thus allowing more complex ones based on configobj to be tested.