Add BidirectionalLookup collection to HeuristicLab.Collections

[abeham]

Currently the collection is implemented in the HeuristicLab.Operators.Views.GraphVisualization namespace. The class however is of general interest and a comparable implementation is .Net does not exist. The existing implementation should be reviewed and moved to HeuristicLab.Collections.

[abeham]

r9000:

• Added BidirectionalDictionary for storing 1:1 mapping and BidirectionalLookup for storing M:N mappings
  • I used HashSets in the BidirectionalLookup instead of Lists, because of the difficulty of removing items when custom equality comparers are used.
• Added unit tests

[abeham]

r9009: Implemented review comments

[mkommend]

r9011: Adapted OperatorGraphVisualization to ignore warnings regarding the obsolete attribute and adapted to the new BidirectionalDictionary if possible.

[mkommend]

r9012: Corrected unit tests for BidirectionalDictionary to changes in r9009.

@abeham: Please have a look over r9011 & r9012.

[abeham]

Thanks for fixing the unit test. I think now that you switched to the new collection in the views project we could revert marking the class obsolete and just declare it internal. What do you think?

[mkommend]

r9019: Removed the obsolete attribute from the BidirectionalLookup in the OperatorGraphVisualization and made the class internal instead.

[abeham]

ok