Proper escaping for popup keys between Swift and JS

Default output null guarding

Fixes display of longpress special keys.

Add version history for 10.0 beta releases for Desktop and Developer

[Android] Disable text suggestions and hide system OSK when resuming app

This handles all transitions where an external app/dialog using the system OSK returns to the Keyman app such as resuming:
* from WebBrowserActivity
* from Android Oreo's "Add to dictionary" dialog

Pressing backspace corrupts cached context with SMP characters

[Android] Tweak back button for WebBrowserActivity

This is a follow-on to #220 that fixed  2 OSK that were appearing when exiting WebBrowserActivity.

* If navigation is possible, backButton navigates back.
* Hide the system OSK so returning to Keyman app won't have 2 keyboards visible

Also ignore build_file_checksums file that Android Gradle 3.1 generates.

Fixes #719 - web compiler not escaping quote char

Allows embedded KMW to retrieve the nextlayer subkey property.

Web - Attachment API manual test page fix

Fixup help.keyman.com.sh to use a version number from environment rather than hardcoded

Update iOS history for intial 10.0 beta release

Moves Web alpha notes to beta, fixes iOS history interactions.