PhysFix - Automatically fixing unit inconsistencies for ROS C++

PhysFix workflow:

1. Run Phys on C++ files. Generate tokens xml, json with errors and variable units
2. Parse the tokens xml into an AST
3. Convert the AST into a CFG
4. Create dependency/dataflow graph from CFG
5. Generate changes for errors using in-scope variables
6. Parse C++ file into XML using srcML
7. Convert changes into XSLT files
8. Apply XSLT file to srcML XML file

Files/Folders

File/Folder	Purpose
/extern/phys	Link to squaresLab fork of Phys as a git submodule
/test	Folder with test files
/src	Relevant physfix source files are here
/src/physfix/parse	Folder with files that turn tokens XML into dependency graph
/src/physfix/parse/cpp_parser.py	Converts tokens XML into python classes. Copied from Phys repo
/src/physfix/parse/cpp_utils.py	Utilities for working with classes from cpp_parser.py
/src/physfix/parse/dump_to_ast.py	Converts classes from cpp_parser.py into real AST
/src/physfix/parse/scope_node.py	Helper class for dump_to_ast.py. Keeps tracks of scopes in a tree-like data structure
/src/physfix/parse/statement.py	Data classes for AST
/src/physfix/dataflow/ast_to_cfg.py	Converts ast into control flow graph
/src/physfix/dataflow/cfg_node.py	Data classes for CFG
/src/physfix/dataflow/reach_def.py	Finds definition-use pairs and reaching definitions from CFG
/src/physfix/dataflow/dependency_graph.py	Converts CFG into dependency graph
/src/physfix/phys_fix.py	Class with end-to-end pipeline, has code for reading/writing xml/xslt files
/src/physfix/run_phys.sh	Helper bash script to run phys using docker