Initial commit for backward-chaining demo
Added README
Added missing quotation mark
Added query
Added some comments/changes
Added small example to figure out variable binding

In backward-chaining
Added ModusPonensRule
Removed BindLinks, added stvs, added AndLink
Removed small example
Added query to agent
Added loop, check for result
Small output format changes
Elaborated in README
Cleaned up some comments
Added printing of inferences so far
Merge pull request #938 from sebastianruder/backward-chaining

Backward-chaining demo