Add early ConfigValidator version
AdvancedSingleRangeNextTest: add whitespace test
Moved tests to new class

Moved two tests from SimpleMultiRangeNextTest to new
AdvancedMultiRangeNextTest class.
Clarified tests

- Added/improved documentation of tests.
- Replaced references (A) with expressions that evaluate to 0, where
  appropriate (A*0).
  That way, tests can assume a fixed value without depending on next
  resolving references to 0.
- Added a multiRangesWithExpressionsOnlyUseLastRange test that is
  separate from the surprisingInteraction test.
AdvancedMultiRangeNextTest: add new tests