Add "conflictsWith" functionality to Filterer library

[chadicus]

What does this PR do?

This pull request adds the confictsWith filter option which allows a user to specify that the given filtered value conflicts with one or more filtered values. If multiple conflicting values are present a FilterException is raised.

Checklist

• [ ] Pull request contains a clear definition of changes
• [ ] Tests (either unit, integration, or acceptance) written and passing
• [ ] Relevant documentation produced and/or updated

[coveralls]

Coverage remained the same at 100.0% when pulling 5ca6340 on chadicus:fea/conflicts-with into a8dec17 on traderinteractive:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 7a02dd4 on chadicus:fea/conflicts-with into a8dec17 on traderinteractive:master.