fix antlr4 generated source output directory
simple driver for digital backends
currently using a test class to generate Schematics
this will be removed once support for JSON import is ready
Merge branch 'issue120-vhdl-codegen' into backend-invocation
Merge branch 'issue120-vhdl-codegen' into backend-invocation
Merge branch 'issue120-vhdl-codegen' into backend-invocation
WIP, testing code gen for registers
vhdl codegen runs design checks, CLI option to disable all checks
Merge branch 'master' into backend-invocation

Conflicts:
	build.gradle
	src/test/java/org/manifold/compiler/back/TestVHDLCodeGenerator.java
remove spurious debugging messages
allow digital backend to accept input from JSON file
checkstyle fixes tho
Merge pull request #139 from mtrberzi/backend-invocation

Backend invocation
hotfix: changed constructor invocation for check
Merge pull request #147 from mtrberzi/hotfix-check

hotfix: changed constructor invocation for check
IN PROGRESS
Implemented parsing for variable references and integer literals
Added basic function invocation parsing
Implemented variable assignment expressions
Added boolean literals