Shell|GUI: Added Preferences, FolderSelection widget, various tweaks
Builder: Order of Doxygen invocations
Shell|GUI: Disable "Running Servers" submenu when there are none
Shell|GUI: A prettier placeholder icon for the toolbar
Shell|GUI: Folder selector can have an extra descriptive label
Shell|GUI: Mirrored map outline on Y axis, various fixes

The Preferences dialog is a bit clearer now, too.
Shell|GUI|Windows: Minor improvements and fixes, added window icon
Shell|GUI: Applied tabs inside the Start Local Server dialog

Divided into basic and advanced settings.
Shell|libshell: LocalServer opens the link, better Preferences handling
Shell|GUI: Check for ports known to be in use when starting a server

The local server dialog will not let the user start a server using a
port that is already in use by another server.

Todo for later: Add a notice of some sort so the user realizes why the
server cannot be started using a particular port.
Shell|GUI: Inform user of a port already in use
Builder|Fixed: Doxygen invocations and chdir
Merge branch 'master' into revise-texture-animation