Fixes custom page, inbox & background images not saving.

Fixes push message with only a cover image offering `view` & `cancel` buttons while it should only display `ok`.

Cleans empty applications randomly generated, prevents empty applications to be saved.

Fixes cover not showing from In-App messages.

Fixes wrong password message not translated.

Improves payload & loading when there is a lot of images & products.

Fixes new QRCoupon not saving QRCode image.

Fixes CSS alignment of move/delete icons.

Fixes 'unexpected error' while using a discount code.

Fixes 'notes' message not saving correctly.

Fixes plans not saving.

Merges pull request from GitHub allowing to choose between Pins or Image to display in the Map.
https://github.com/Xtraball/SiberianCMS/pull/372

Adds hint about optimal size images to upload.