initial AST entities
tuple expressions
Merge branch 'master' of file:///home/mtrberzi/whdl/public
add Variable and Scope classes
todo: exceptions, test cases
add exceptions for Variable, Scope, and friends
delete old frontend code, for cleanup purposes
Merge branch 'master' of file:///home/mtrberzi/whdl/public

Conflicts:
	src/main/java/org/whdl/frontend/syntaxtree/TypeValue.java
	src/main/java/org/whdl/frontend/syntaxtree/Value.java
add hashCode() and equals() to NamespaceIdentifier
move members to top of class in Variable
add file scope to CompilationUnit
by the way, this entire branch deals with #25
change List to Set in CompilationUnit
change eval() to evaluate()
fix multiple nits on #25
fix nonsensical Scope parameter on CompilationUnit.populateScope()
reformatting of Variable, no syntactic changes
fix suboptimal list equality check in equals()
add equals() to VariableIdentifier
test cases for Variable
add test for VariableIdentifier.equals()
reorder definitions