Add Keypad mapper to taginfo

[dkniffin]

There's a new feature on taginfo where you can see which projects are using which tags. Example: http://taginfo.openstreetmap.org/projects

The way to integrate your project is by creating a json file with the details of what tags keypad mapper is using and then add it to a txt file. Details about this can be found on the wiki page: http://wiki.openstreetmap.org/wiki/Taginfo/Projects

I think for keypad mapper, the only tags used are addr:housenumber and survey:date, so I might take a stab at this and submit a pull request