Start work on parsing Python annotation syntax

Note: still many test case failures!
Use Foo[...] syntax for generic types
Basic support for "# type:" annotations

Error handling and other special cases still not there.
Remove obsolete test case
Parse "# type" annotations with multiple types
Add test case
Remove obsolete test cases
Remove special syntax for casts
Remove type applications and literal types
Remove for statement type annotations
Remove test cases that use custom syntax
Remove generic function syntax
Remove unused code
Remove unused code
Remove unused code
Update test case
Remove test cases for old syntax
Update test cases
Update test case
Fix parsing of lambdas