Server: Relocated the "server" domain subfolder to the server executable

The engine.pro (client) executable no longer has the capability to
run as a server.

Todo (long-term): keep separating more server-specific functionality.
Renamed the "engine" project to "client", moved api headers

The "engine" project is now officially designated the Doomsday Client
executable. The public API headers were moved one directory level
upwards so that they can be comfortably shared between the client and
server executables.
Example Plugin: Updating the example plugin for inclusion in builds
Renamed "plugins/exampleplugin" to "plugins/example"

Now consistent with the naming of the other plugins.
Fixed: DENG_API_EXCHANGE requires string.h

The call to memcpy() is done in the macro, so making sure the proper
header is included.
DENG_API_EXCHANGE needs string.h (for memcpy)
Merge branch 'master' into separate-server

Conflicts:
	doomsday/plugins/example/doc/readme.txt
Cleanup
Snowberry: Launching doomsday-server

The server needs to be launched with the doomsday-server executable,
and it needs to use a different runtime folder than the client (as it
lacks many subsystems and thus would fail to retain client-only cvars
etc.).

Also bumped Snowberry version to 1.6.
Fixed|Snowberry: Missing space in options string
Documentation|Client: Mass update to .cpp/.h banners to adhere to template
Documentation|Server: Mass update to .cpp/.h banners to adhere to template
Documentation|Client: Continued source header update
Documentation: Cleanup
Client: Cleanup
Fixed|Windows: Fixed build, .rc include paths
Windows: Script for generating a Visual Studio solution

"build\win32\qmake_msvc.py" is a script that generates a full Visual Studio
solution with a .vcxproj for each subproject. It depends on envconfig.bat.
The solution is always placed in a folder called "doomsday-msvc-build" at
the repository root.

qmake_msvc.py must be called whenever the .pro/.pri files change. The .sln
and .vcxproj files are then rewritten -- manual edits will be gone!

The solution automatically deploys all built binaries into the
"distrib\products" folder. The user is expected to 1) copy the required
dependency .dlls to products\bin, and 2) define the appropriate launch
command line and options (which are persistently then stored in the
.vcxproj.user file).
Windows|qmake: Added instructions into qmake_msvc.py
Fixed: Missing header in release build (in b_context)
Fixed: Missing header in dd_input