Revamped the typing system.

Implemented isAssignableFrom almost according to spec.
Refactored clients of the typing system.
Added accurate Constant computation.
Rebuilt a couple of inspections.
Removed the GoUnderlyingType tree.
A lot of other cleanups.
Also Fixes #858
Fixed getRepresentation(GoType, GoFile) for typed constants.
Marked some tests as @Ignore
Don't use java 1.8 API
Import cleanups.
add test cases for #686, #811, error.Error()
Merge pull request #981 from bronze1man/pr-test1

add test cases for #686, #811, error.Error()
Fix a infinite recursion when discovering PromotedFields.
fix #979, add testCallOrConvExpressResolveToConv
Merge pull request #980 from bronze1man/pr-979

Temporary fix for #979
add a test case of a bug that two go test files can not resolve each other.
Merge pull request #982 from bronze1man/pr-test1

add a test case for #599 Symbols from *_test.go files in the same package should be shared.
More work on constant expression computation.
Sort the package list in the test runner dropdown box
Merge pull request #983 from horkhe/master

Sort the package list in the test runner dropdown box
Resolve map composite literal keys to constants.
Make the Composite resolve work again.
Fixed a failing test.
add constantExpressions test cases from golang spec
add test case for #989