Add a fake User-Agent to tasks fetching remote resources (bug 1018279)

Sadly necessary because some hosts blacklist the default
UA used by python-requests :(
move tests
Merge pull request #2134 from diox/validator-user-agent

Add a fake User-Agent to tasks fetching remote resources (bug 1018279)
Display notification on pages only the owner can edit (bug 939075)
update app-validator
Merge pull request #2137 from eviljeff/patch-9

update app-validator
Merge pull request #2136 from diox/only-app-owner-message

Display notification on pages only the owner can edit (bug 939075)
Return receipt for in-app payment (bug 944522)
Merge pull request #2126 from kumar303/inapp-receipt

Return receipt for in-app payment (bug 944522)
stop robots going to payments (bug 1020881)
Merge pull request #2139 from andymckay/1020881

stop robots going to mozpay
suggested settings cleaning
and don't use SERVE_TMP_PATH on prod servers (bug 1020861)
Removed APP_PREVIEW setting
Merge pull request #2140 from andymckay/mat-settings

suggested settings cleaning
remove old tests for code thats about to be deleted
Fixed typo in docs
Moved abuse to mkt/
Merge pull request #2142 from andymckay/remove-test

remove old tests for code thats about to be deleted
fix test