Replaced try-catch with calls to respondsToSelector to make the check more explicit. 

Added some comments and diagnostic code.

Enabled Keyman to deal with selection changes resulting from keyboard navigation. Tried a solution for Word in Safari, but commented it out. Added Firefox to the list of browsers that need to try to detect whether editing is in Google Docs. 

Added special logic to handle Google Docs in Chrome, where multiple characters cannot be inserted simultaneously.

Solved Mail compatibility problems using regex to ensure that "preChar" starts with a base character. Added MS Word as a "legacy" product to make it work correctly.

Added fallback code to convert percent-escapes in URL for downloaded keyboard for version of OS where stringByRemovingPercentEncoding is not available.

WIP: Replaced calls to NSColor colorWithRed:green:blue:alpha with calls to colorWithSRGBRed:green:blue:alpha because the former was not available until OS version 10.9

WIP: Work to deal with handling a Q_BACK that tries to insert a combining mark instead of a base character (along with its combining marks). This causes compatibility problems in some apps (e.g., Mail)

addKeyboards parameter property:  'language' -> 'languages'.

Sets init param 'attachType' to 'auto' for all devices.

[Mac]: Prevent Keyman processing command keys

Cherry picked a few small changes from "mac compatibility" branch to fix bug whereby command keys were sometimes causing characters to be output.

Tried adding Oxygen XML editor as a "legacy" app, but it's problems were more severe, so I commented it out.

Added code to prevent sending an extra delete-back in Google Chrome when it inaccurately reports a text selection.

name/id mismatch in MergeKeyboardInfo

Move KMBM variable out of KV member in keyboards to match compiler behaviour

Fixup attachType for web debugger in Keyman Developer

Addresses the recent iOS image asset requirement change.

Removes the 'free' set of asset images and attaches the newly required 'marketing' 1024x1024 icon.  Addresses #371.

Prevented processing of Command keys. Fixed timing related problems when repsonding to actions that require us to get the context again. In Safari Google Docs, fixed problem when typing replaces selected text (once we've managed to detect we're in Google Docs). Added Xcode to the list of apps that don't let KM know about arrow keys and/or mouse clicks that might affect the context.

WIP: Most "legacy" app and Google Docs issues now dealt with pretty well. A few more issues to look at and some code cleanup to do.

Refactor longpress logic so key text is not confused with key code

`String.fromCharCode()` has a limitation to Unicode characters in the BMP. Change to `String.kmwFromCharCode()` to handle entire Unicode range.

Also clarified how default key codepoints are processed.

KeyboardHarness changes:
- Change text area font on keyboard change
- Added U_10481 to test longpress keyboard.
- Remove test tchad keyboard

Update comments explaning how control codes U_0000 to U_001F and U_0080 to U_009F are suppressed.

Also updated longpress test keyboard to test control codes.

* Fix accessing AltGr shift layer
* Fix AltGr OSK layer to display as "Alt Ctrl"
* Fix how Unicode control characters are filtered out, so U_00A0 can be displayed

Rework of KMW keyboard registration + default keyboard selection.

Mobile default-layer shifting regression fix