Redefined the ResolveStates class
A lot of changes to the resolving infra.

Resolve imported packages and some exported symbols.
Resolving package imports works.
Have to add import test cases.
Added more reference caching. This will speed up the thing tremendously.
Added package import test cases.
Reenabled a bunch of var resolutions.
Fixed a parsing test.
More work on the type resolving.

Parsing of composite literals which contain an imported type is broken.
Default imports is also broken but this is broken in general.
Fix the builtin symbols better
Added builtin package to a bunch a tests.
Updated a bunch of parsing test cases.
Added builtin package to the completion test cases.
Added function call or conversion resolving.
Added resolving of struct key fields.
Improved resolving of StructField keys.
Fixed more resolving tests.
Cleaned up more code.
Updates parser (just 80 failing tests remaining)
Updated some completion tests.
Broken tests down to 50.
Updated the package completion tests.
Fix a completion test case.
Fixed the struct completion visibility rules.
More tests fixed.