Inntroducing a new feature in Tamarin: automatic generation of sources lemmas.
To enable source lemma generation, Tamarin needs to be launched using the command line parameter --auto-sources.
The theory behind this PR is explained in the upcoming ESORICS'20 paper Automatic generation of sources lemmas in Tamarin: towards automatic proofs of security protocols.

* Started implementing auto-generated source lemmas

* first running version of auto-generated source lemmas

* auto-generated source lemmas in diff mode

* fixed spurious wellformedness errors

* fixed encrypted subterms, consider other input facts

* do not consider variable as deepest encrypted subterm

* use all conclusion facts

* add conclusion index to out annotation

* unfolding variants if necessary

* fixed protected subterm computation

* handle rule names correctly, pretty print variant rules as rules modulo AC

* examples

* README for examples

* Added auto-sources regression test