[developer] Restrict modifier options to a small set by default in touch layout editor

Trap errors if Keyman Desktop is not installed when trying to install a keyboard

[developer] Avoid crash if online update already running

Merge pull request #811 from keymanapp/developer-layout-editor-does-not-remove-empty-row-completely-254

Ensure only one key is selected so modifying or deleting it doesn't break JSON

[developer] When importing a KVK into touch layout, treats sp, width and pad as strings

[developer] When importing a KVK into touch layout, treats sp, width and pad as strings to mitigate #743

[Mac] 705/709/791 Fixes to configuration/download windows

Ios/json parsing miliseconds

Ios/case insensitive alpha list

Still need to investigate why some links to help.keyman.com/... don't work in download window. Also, this check-in contains some commmented-out code to try to get mouse pointer to change over hyperlinks. Need to get it working or revert (possibly need to report as a separate issue). Also, it would be nice for there to be some user feedback when loading pages, which can be quite slow at times.

This allows "Go to keyman.com" button to work correctly.

[developer] Update BCP 47 selector in Keyman Developer to support lookup and more stringent checks

[developer] Fixes crash after save or source view change in OSK Editor

[Web] AltGr emulation fixes

Fix loop in test for match and nomatch validity

Fix OSK missing keys on older Android configurations

[developer] Workaround for use-after-free in Delphi string management causing EInvalidPointer exceptions

Fixes #786

Fixed call for finishing activity when cancelling keyboard download dialog