Merge pull request #1783 from ngokevin/iarcversion

workaround set_iarc_storefront_data in rare case of missing version (bug 967638)
Ensure apps cannot re-use IARC certificates (bug 972437)
remove pre-approval code (bug 748827)
Merge pull request #1567 from andymckay/cleanup-paypal

remove pre-approval code (bug 748827)
add this back in for the moment (bug 748827)
fix migration (bug 748827)
exclude waffle from jingo loader (bug 963513)
Slightly improve translations documentation
Merge pull request #1787 from diox/docs-translations-improvements

Slightly improve translations documentation
update pfs for flash; bug 974132
Fix URL for the app preview posting API (bug 974957)

DRF automatically generates it, and we want/documented /preview/,
not /preview_list/ !
Merge pull request #1790 from diox/fix-api-previews-url

Fix URL for the app preview posting API (bug 974957)
point mkt stage towards iarc demo