Generate xml documanetation for JSIL.Meta
Fix generic variance checks failing to find matching interfaces (#452)
Fix issue #453:
  Fix HashSet not implementing ICollection`1
  Fix HashSet.Add not having a definition for ICollection`1
Merge pull request #451 from iskiselev/MetaDoc

Generate xml documanetation for JSIL.Meta
Merge

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extra : amend_source : 4fbcfd8fd5aa4c397c0cb89b3eb0176821cf768a