xz1919: WIP added frontend and backend implementation for do-while, for, break, continue, and switch(only frontend)

sx119: parser.g4: add back print expr rule, debuged stat_with_end, functionJunkAfterReturn.wacc: changed as semantic error

sx119: .gitlab-ci.yml: added seperated test for testing parser, parser.g4: added rule of stat_with_end, failing test

sx119: test/example/invalid/ valid/: change BitIntTest to semantic error, Parser.g4: disallow multiple top level begin, function end with exit or return

xz1919: added a log folder for logging the errors encountered by parser/lexer. Restructured folders.

sx119: FullLexer.g4: change int_liter to represent only positive num, FullParser.g4: add PLUS INT_liter in expr rules

sx119: src/test/: added rule identifier, separate rules in expr gramma, implemented prototype of semantic checker using visitor

Revert "sx119: *.g4: changed priorities in rules, passed all manual test, systematic test to be written in yml"

This reverts commit c453cd26.

sx119: *.g4: changed priorities in rules, passed all manual test, systematic test to be written in yml

xz1919: restructured folders to include a main and a test folder, formatted .g4 files and corrected the COMMENT lexer pattern to only exclude EOL

sx119: modified antlrBuild: using FullLexer FullParser, new file: FullLexer FullParser include rules from spec