Refine bounds checking to prevent putting the internal frame in a position where it could not be dragged back to visible area.

Also, prevent a NPE occurring on Macs since the browser extension have been re-enabled.
When UI is Mac, introduce a desktop manager using a most-recent-use order
for its panels and disable iconify/deiconify to prevent problems
occurring because Aqua desktop manager is not used.
Merge pull request #36 from marcpa00/bounds-aware-desktopmanager-tweaks

Refine bounds checking of DesktopManager
Makes media type combo generic
Revert removal of help icon from header inspector
Corrects the header help link
Removes unnecessary links
adds test for the new media type combo box
Update tests
Adds media type content
Improvement on PR, and setting for activating most recently used panel
Adds syntax highlight support for json
Bump up rsyntaxttext area to 2.0.7
Merge branch 'next' into record-internal-browser-SOAP-1516
SOAP-1516 Add a navigation bar