Bug 963917: reduce Gallery memory use (and fix leak) while scanning

force software canvases for thumbnail and preview creation with willReadFrequently

Free canvas memory after creating a thumbnail

Make sure our thumbnail blobs are file-backed not memory-backed

update mediadb docs
(cherry picked from commit 4b5eaa4a2823d8961b80a3b975b1eeed92b9fcb7)

Conflicts:

	apps/gallery/js/MetadataParser.js
	apps/gallery/js/gallery.js
Bug 930563 - [B2G][L10n][Clock] Chinese Traditional: Highlight date instead of first number displayed.
Bug 897873 - [Buri][WIFI][language]Secrecy information of AP are not translated automatic
Bug 960705 - [clock][l10n] Close button should say Stop instead; r=reviews
Bug 968071 - Taken/Shoot date in image/video info not localizable

This approach let us reuse an existing string, so it can be ported to
1.3

Note that this also changes the en-US format from mm-dd-YYYY to
mm/dd/YYYY
Bug 971631 - Correct screenshot dimension
Bug 951586 - [DSDS][STK] Suport multiple cards in system STK code, r=timdream
Bug 971647 - Ignore load script error in blanket
Bug 968220 - Add a "Developer HUD" sub-menu in "Developer". r=vingtetun
Merge pull request #16091 from jankeromnes/developerhud

Bug 968220 - Add a "Developer HUD" sub-menu in "Developer". r=vingtetun

Note that this also deletes the Grid overlay.
Bug 969587 - Make customization run without ICCHelper present
Bug 969587 - Integration tests for FTU variant customization
Merge pull request #16212 from gnaneswar/Issue_960705

Bug 960705 - [clock][l10n] Close button should say Stop instead; r=mcav
Merge pull request #16186 from mcav/bold-date

Bug 930563 - [B2G][L10n][Clock] Chinese Traditional: Highlight date. r=gnaneswar
Merge pull request #16149 from davidflanagan/bug963917-3

Bug 963917: reduce Gallery memory use (and fix leak) while scanning r=dkuo
Merge pull request #16097 from qdot/969587-variant-with-no-icc

Bug 969587 - Run variant customization with no icc
Bug 966215 - Allow make test-integration to specify TEST_FILES. r=gaye
Merge pull request #16071 from flodolo/bug968071_mediainfo

Bug 968071 - Taken/Shoot date in image/video info not localizable
Bug 968049 - Don't try to reload a null URL when reviving crashed tabs
Add calendar-1.4-visual-refresh to travis branches

We can remove this once the branch lands on master.