Moved apps/addons/ to mkt/webapps/ (bug 1021189)
Removed defunct activity link from lookup tool
Verify inapp id in receipts (bug 1021359)

- Add inapp_id to inapp product receipt
- Update receipt generation tests
- Verify inapp_id against contribution during receipt verification
- Update receipt verification tests
Merge pull request #2190 from JaredKerim-Mozilla/1021359

    Verify inapp id in receipts (bug 1021359)