Split parse_statement() into more methods

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
Fix bug in unittest (duplicate method name)

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
Minor Variable __init__() cleanup

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
Add Namespace copy() method

Signed-off-by: Esben Haabendal <esben@haabendal.dk>