Change inapp public ID to UUID (bug 1035448)

- Add guid field to inapp
- Update APIs to use guid
- Update inapp product pages in devhub to use guid
- Update purchase to use guid
- Update receipts to use guid
- Update tests
Merge pull request #2421 from JaredKerim-Mozilla/1035448

    Change inapp public ID to UUID (bug 1035448)
set status bar colour for FxOS (bug 1056257)
Update In App Product Documentation to use UUID (bug 1056274)
Merge pull request #2433 from JaredKerim-Mozilla/1056274

Update In App Product Documentation to use UUID (bug 1056274)
forgot premium_type in feed app serializer (bug 1055742)
Merge pull request #2431 from cvan/theme-colour

set status bar colour for FxOS (bug 1056257)
add device filtering to apps of the feed (bug 1054381)
Merge pull request #2429 from ngokevin/feeddev

add device filtering to apps of the feed (bug 1054381)
move es refreshes into get methods in test views
move DEVICE_CHOICES_IDS to constants/applications
generate_apps doc blurb
add user to app serializer for feed
Commit from Mozilla Verbatim by user a.polivanchuk@outlook.com.: 250 of 1966 strings translated (1 fuzzy).
clean up feed filtering
Commit from Mozilla Verbatim by user civas.: 1966 of 1966 strings translated (0 fuzzy).
filter for public apps for the feed, don't slice until filter (bug 1056426)
Merge pull request #2435 from ngokevin/filterfeed

filter for public apps for the feed (bug 1056426)
Populate guid for inapp products (bug 1056363)
Merge pull request #2437 from JaredKerim-Mozilla/1056363

Populate guid for inapp products (bug 1056363)