WebContent: Start work on browser process separation :^)

The "WebContent" service provides a very restricted instance of LibWeb
running as an unprivileged user account. This will be used to implement
process separation in Browser, among other things.

This first cut of the service only spawns a single WebContent process
when someone connects to /tmp/portal/webcontent. We will soon switch
this over to spawning a new process for each connection.

Since this feature is very immature, we'll be bringing it up inside of
Demos/WebView as a separate demo program. Eventually this will become
a reusable widget that anyone can embed and easily get out-of-process
web content in their GUI.

This is pretty, pretty cool! :^)

Demos/WebView/CMakeLists.txt

@@ -0,0 +1,13 @@
+set(SOURCES
+    main.cpp
+    WebContentView.cpp
+    WebContentClient.cpp
+)
+
+set(GENERATED_SOURCES
+    ../../Services/WebContent/WebContentClientEndpoint.h
+    ../../Services/WebContent/WebContentServerEndpoint.h
+)
+
+serenity_bin(WebView)
+target_link_libraries(WebView LibGUI)