basic opt-in stats gathering

[ckdake]

By default:
* check in for most recent version (doesn't report anything back) once a week
* log this on GMC so that we can get # of hellos per week

Optionally "Continue with stats" button
* number of users
* number of groups
* number of items
* number of albums
* list of activated modules
* platform info (mysql version, php version, anything else?)
* each G3 generate a random number that it stores in it's DB

keyed on unique ID, we should store:
* first "ping"
* most recent "ping"
* collected information

[bharat]

Milestone 3.0 Final deleted

[bharat]

Don't forget to add a nice admin page.