reworked original 2.x version of xrange into range

Fixes #50.

added applicable test from stdlib
added convenience methods to iptest/assert_util.py to mimic unittest
added slice operator
added == != < <= > >= operators
added `__contains__` method
added count and index methods of collections.abc.Sequence
changed start, stop and step to be attributes
added `__hash__`
added support for objects implementing `__index__`
Converter.TryConvertToIndex does not ignore throwOverflowError parameter

Outstanding: pickle testing - it depends on itertools which depends on missing language features
When reviewing, go for second commit otherwise rename obfuscates changes.

Test results:
```
rejap@WIN-CUE1I6EN9JB ~/github/ironpython3/bin/Debug
$ ./IronPythonTestConsole.exe  IronPythonTest -noh -labels -full -test:IronPythonTest.Cases.IronPythonCases.test_range
Runtime Environment -
    OS Version: Microsoft Windows NT 6.1.7601 Service Pack 1
  .NET Version: 4.0.30319.18444

***** IronPythonTest.DLL
***** IronPythonCases
***** IronPythonTests
***** test_range
>>>   0.00s testing test_attributes_from_stdlib
>>>   0.27s testing test_comparison_from_stdlib
>>>   0.40s testing test_contains_from_stdlib
>>>   0.47s testing test_count_from_stdlib
>>>   0.55s testing test_empty_from_stdlib
>>>   0.56s testing test_index_from_stdlib
>>>   0.71s testing test_invalid_invocation_from_stdlib
>>>   0.94s testing test_issue11845_from_stdlib
>>>   1.02s testing test_odd_bug_from_stdlib
>>>   1.05s testing test_range
>>>   1.09s testing test_range_collections
>>>   1.11s testing test_range_corner_cases
>>>   1.12s testing test_range_coverage
>>>   1.16s testing test_range_equal
>>>   1.19s testing test_range_from_stdlib
>>>   1.23s testing test_repr_from_stdlib
>>>   1.24s testing test_reverse_iteration_from_stdlib
>>>   1.26s testing test_slice_from_stdlib
>>>   1.30s testing test_strided_limits_from_stdlib
>>>   1.31s testing test_types_from_stdlib
>>>   1.45s testing test_user_index_method_from_stdlib

21 tests passed
Tests run: 1, Passed: 1, Errors: 0, Failures: 0, Inconclusive: 0
  Not run: 0, Invalid: 0, Ignored: 0, Skipped: 0
Elapsed time: 00:00:13.2410000
```