Add "Revealer" seed backup plugin (#4228)

* revealer commit

* fix seed font, added license

* fixed strings for translation

* better calibration instructions, fixed position

* removed html from translatable strings, fixed typo

* Added monospace font for codes, cleaned up redundant font formatting

* Monospace font for codes and respective license

* fix redundancies, typos

* inner function to only move forward if no exception

* paint QR qith QT to not depend on PIL
catch exeptions when creating a digital Revealer

* clarity

* Added SourceSans font License

* fix fonts paths, typo

* broke long lines, changed some words for clarity,
removed redundant font license

plugins/revealer/__init__.py

@@ -0,0 +1,17 @@
+from electrum.i18n import _
+
+fullname = _('Revealer')
+description = ''.join(["<br/>",
+    "<b>"+_("Do you have something to hide ?")+"</b>", '<br/>', '<br/>',
+    _("Revealer is a seed phrase back-up solution. It allows you to create a cold, analog, multi-factor backup of your wallet seeds, or of any arbitrary secret."), '<br/>', '<br/>',
+    _("Using a Revealer is better than writing your seed phrases on paper: a revealer is invulnerable to physical access and allows creation of trustless redundancy."), '<br/>', '<br/>',
+    _("This plug-in allows you to generate a pdf file of your secret phrase encrypted visually for your physical Revealer. You can print it trustlessly - it can only be decrypted optically with your Revealer."), '<br/>', '<br/>',
+    _("The plug-in also allows you to generate a digital Revealer file and print it yourself on a transparent overhead foil."), '<br/>', '<br/>',
+    _("Once activated you can access the plug-in through the icon at the seed dialog."), '<br/>', '<br/>',
+    _("For more information, visit"),
+    " <a href=\"https://revealer.cc\">https://revealer.cc</a>", '<br/>', '<br/>',
+    
+])
+available_for = ['qt']
+
+