Fix ScriptToFunctionTest, and add it to AllTests.
Refactor file handling.

* Remove filters from natlab.toolkits.filehandling, not used anywhere
* Merge filehandling.genericFile into filehandling.
  (Fix imports everywhere.)
* Remove {get,set}{Name,FullPath} methods from Program; use getFile()
  instead. You can still do Script.getName().
* Rename GenericFileMatlabTools to GenericFileFilters
* Simplify logic in FolderHandler.addPath
  (future work: add tests, and make sure it works with nested packages)
Add some tests for FolderHandler.

Also introduced a neato MockFile class for testing. (There's BuiltinFile
which seems to be the same idea and used by the natlab.refactoring tests,
but it seems kind of complicated...)

It would also be nice to rename lookupSpecializedAll and
getAllSpecialized to be less confusing.