Doc: Add supported platforms information for Qt 5.10

  - Mention the use of Windows 10 Creators Update in CI
  - Replace openSUSE 42.1 with 42.2
  - Update CI-tested compiler on Ubuntu
  - Drop macOS 10.10, add 10.13, and mention Xcode versions
  - Drop iOS 8,9 and support for 32-bit targets. Add iOS 11
  - Add tvOS and watchOS (as technology preview)
  - Added all Darwin platforms under a dedicated section
  - Mention Qt for Device Creation/Boot2Qt configurations
  - Add Windows7-x86_64 as a host configuration for QNX
  - UWP: Add MSVC2017 as a CI-tested compiler
  - Use 'x86, x86_64, armv7' etc. consistently to describe
    platform architecture.

Merge 'Mobile Platforms' section with desktop platforms as most
of them are not restricted to any specific segment. Keep
'Embedded Platforms' as a separate section still.

Change-Id: Iafe76dd8f95a9fd8c9ba3fd0a077d7087df1c258
Reviewed-by: Jake Petroules <jake.petroules@qt.io>