Added basic Expression classes

A lot of details, declarations and implementations are missing because
of unresolved discussions (statements vs. assignment expressions,
primitive operations vs. macros, etc.) as well as VariableIdentifier not
holding a ref to Value for function calls.
FunctionExpression Branch
Expression && LiteralExpression
Modified tests to remove FacadeExpression
Expression and LiteralExpression

- Moved FunctionInvocationExpression and pals to another branch, no
longer in this commit
- Changed some of the tests to use LiteralExpression
- Changed Value->TypeValue in TypeMismatchException
Formatting
Removed doc blocks
Reverted TypeMismatchException
add Namespace class, basic functionality, tests
re. #26
add Namespace class, basic functionality, tests
re. #26
Merge branch 'namespace' of github.com:MurphEngineer/whdl into namespace

Conflicts:
	build.gradle
Merge pull request #39 from maxqchen/master

Added basic Expression classes
Merge branch 'master' of file:///home/mtrberzi/whdl/public into namespace
Added convenience NamespaceIdentifier constructor
Merge pull request #46 from lucaswoj/namespace-string

Added convenience NamespaceIdentifier constructor
add Namespace.containsIdentifier()
Merge branch 'master' of file:///home/mtrberzi/whdl/public into namespace
nit-picking of previous work, and test cases
correct erroneous removal and ignore of buildfile
refactor containsIdentifier to isVariableDefined
remove variable search functions
use private and public scope instead
add tests for exception classes
add tests for exception classes