code completion: reduce relevance for non class fields and for java.*, scala.* packages

code completion: reduce relevance for non class fields and for java.*, scala.* packages

* Added CompletionOrderTests in CompletionTestSuite for testing completion proposals order
* Added two test related to #1002343
* Fixed relevance algorithm

With this changes order should be:
* Locals
* Fields
* Orders from old algorithm, but symbols from java package take -15 penalty and from scala package take -10 penalty

I decide to penalize java and scala package because it`s symbols (also fields and methods) are less `local` then symbols
from client code.

Fixes #1002343
grammar nitpicking:

The implementation _is_ based ... that _is_ used in _JDT_ to ...