fix #858
fix a NullPointerException look like #950
Merge pull request #966 from bronze1man/pr-858

fix #858
Fixes #973.

Adds a NPE guard.
Fixes #975.

Adds a NPE guard for the builtin package. However the builtin package SHOULD always be available (from the SDK) so this means that the there is no SDK configured..
Another NPE guard.
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.
Sort the package list in the test runner dropdown box