Fix for extra paths inside workspace

[AlexanderSher]

Fix #281: Support "go to definition" for namespace packages
Fix #466: Fix "go to definition" and resolving imports

The fix is to put user search paths in front of workspace directory so that modules inside extra paths can be used as roots for packages

[jakebailey]

If I have a folder structure like:

root
│   main.py
│
├───foo
│       __init__.py
│
└───some
    └───other
        └───foo
                __init__.py

Will adding some/other to the user search path then prevent the import of the first foo?

[AlexanderSher]

Yes, PathResolver will pick the first module, which in this case would be some/other/foo.

[AlexanderSher]

What we can do is add foo to root as some.other.foo and to root/some/other as foo, but preserve old resolution order. This will still fix the bugs, but have more "natural" style of resolution.

[AlexanderSher]

Unfortunately, this idea won't work because of the #468. If file is added to several roots, there will be more than one module name associated with it, which isn't supported by analyzer.