OpenBoard new 1.4.5 v17.1

The main changes intended to be done before a proper release are done, now work on when ready issues can start.
Focus will be on fixing bugs and preparing for a release on F-Droid.
A new name for the Keyboard will be necessary, you're welcome to post suggestions in #3 or in the discussion section.

Changes since v17:

• increase minimum Android version to Android 5.0 / Lollipop (#343)
• improvements to inline autofill by @arcarum (#371, #386, #392)
• allow customizing symbol layouts (in advanced settings / experimental)
• fix a bunch of issues
  • broken russian layout (#370)
  • flashing toolbar keys (#374)
  • crashes (#373, #390)
  • suggestions background for dynamic colors by @BlackyHawky (#375)
  • some minor things