Button event signatures fixed for consistency

Button event signatures now "handlerMethod(eventSource, eventData)"
where eventData == { button }
changelog.txt update for button event signatures
changelog.txt update for Button event signatures
changelog.txt update for event signature change
Merge remote-tracking branch 'origin/Touch-Bug-Fix'
Merge remote-tracking branch 'upstream/master'
changelog.txt update for TileSource event sigs
Merge branch 'master' into Button-Event-Signatures
Post-merge quick fix
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' into Button-Event-Signatures
Merge pull request #241 from msalsbery/Button-Event-Signatures

Button event signatures fixed for consistency (#224)