Add tests for operators, field accesses, assignment
Add test for duplicate/wrongly named main methods
Require programs to have a main method
Visit first parameter of array access
Test for calling the main method, disallow main method's parameters to be accessed
Remove uglinesses in the code
Add wildcard import
Merge pull request #110 from jspam/041-tests-tests-tests

Implement remaining semantics checks and add many more tests