Allow configuring what items to show in the map balloons

[jidanni]

Some people just want to see the date, other people just want to see the LAC, other people want to see the date the time the LAC and the CellID.

Therefore, on the map, when we tap a node and its balloon pops up, what should be included in that balloon should be adjustable by a new map preference item.

There could be one checkbox corresponding to each column in the database that we could show.