Tidied up the code a bit.

Split the engine off into a separate Engine class and reorganised the code into more specialised packages.

Removed the profiler

Some more unit tests, including whether the output of toString() can be parsed back in.

Some documentation changes.

Updated the documentation

The details of the built-in predicates and the retract query were in the wrong place in the README

Fixed the README

Renamed the project to Jatalog - it's more catchy.

Added a help and a timer command to the shell and fixed the command parser.

Fixed some of the javadocs.

Added an optimization where, in expandStrata() the variable newFacts is now an instance of `IndexedSet`.

Changed the syntax of the delete statement to <query>~

Simplified the API:

getRelevant() rules has now been renamed to getRelevantPredicates().