Always show the Legend button.

Also clean up some jshint warnings.
Merge pull request #393 from NICTA/alwaysShowLegend

Always show the Legend button.
message fix
Merge pull request #394 from NICTA/messageUpdate

message fix
typos
Merge pull request #395 from NICTA/messageUpdate

typos
Show a message when a group is empty.
Merge pull request #396 from NICTA/emptyGroupMessage

Show a message when a group is empty.
Improvements to cache population.
Merge pull request #397 from NICTA/populateCacheImprovements

Improvements to cache population.