Feat: Started implementing branch based leder state (#324)

* Feat: value transfers are working

* Feat: tangle now detects invalid transactions

* Refactor: refactored some code

* Feat: finished unit test for value transaction

* Feat: added ledger state (reads information from value tangle)

* Refactor: refactored some code

* Feat: finished refactoring isTransactionSolid method

* Feat: added RealityId model for parallel reality based ledger

* Refactor: moved Output to tangle and introduced branches

* Refactor: refactored some code

* Refactor: renamed "NEW" color

* Feat: started adding branches