Added class 'Error' in tree
Added mutable fields for static analysis and interpretation.
Tree keeps data of static analysis.
Remade example of tree for static analysis.
Merge branch 'master' of https://github.com/mbryksin/projectJANE
Merge and added unit testing.
Fixed bag of moving packages.
Update tree.
Update SA.
Added new tests
migration errors
merge unit tests conflict
Merge branch 'Lozov-Petr-SA'