Ltlf2dfa

* Introduce `PLTLfWeakBefore` and `PLTLfPastRelease` support
* Hotfix problem on translation of the Once operator
* Increase code coverage

* Introduce optional argument to `to_dfa()` method for DFA in MONA output
* Add parsing support for `LTLfLast()` and `PLTLfStart()` keywords
* Some fixes
* Increase code coverage

* Include *.lark files in the package build
* New online version: [http://ltlf2dfa.diag.uniroma1.it/](http://ltlf2dfa.diag.uniroma1.it).

* Refinement of all the grammars. Extensive improvement of the parsing.
* Introduce interfaces and class hierarchy for the logic modules.
* Several bug fixes and introduce testing.
* Introduce of docs.
* Introduce Continuous Integration.
* Refactor translation feature.
* Replace parsing library PLY with Lark.

* Online version: [http://ltlf2dfa.diag.uniroma1.it/](http://ltlf2dfa.diag.uniroma1.it).