reformat DocString
Implement ST16 + Bugfix ST8
bugfix direct byte - TODO: direct word
implement BLO/BCS/LBLO/LBCS and BHS/BCC/LBHS/LBCC branch
* Implement JSR

* Use objects instead of strings to address registers
* set STACK_PAGE to 0x7e36 (?)
update unittests (work in progress)