Implement ignoring/unignoring of places

[jimburton]

Users should be able to "ignore" and "unignore" a place, meaning that the place in question doesn't show up in any activity (BigArrow, List or Map) until unignored. This is a pretty big feature, as it requires adding a database to the app and making some new screens.

A widget for ignoring should appear on the PlaceDetailsActivity. Tapping this adds a row to the database in a table that probably only needs two columns, _id (autoincrement column) and placeid. Ignored places should be filtered out of the PlaceSearch results. Since we now want to present the 20 nearest non-ignored places, the easy way round it would be to select 20+count(ignored), remove any ignored places from the results then present the nearest 20. This is a nasty kludge though, because we will often be retrieving more records than we need and if someone ignores hundreds of places it would be impractical.

We then need a new Activity that lists the ignored places with an option to unignore them, removing the record from the database.