Refactor modules, closes #223

* All modules are sandboxed now
* All images,sounds,fonts,translations and styles were moved to "data" folder
* Reorganize image files folders
* Remove unmaintained modules: client_particles, client_shaders
* Implement new automatic way to load styles and fonts
* Add hide/show offline option in VipList
* Add invite/exclude to/from private channel in players menus
* Many other minor changes

data/styles/10-windows.otui

@@ -0,0 +1,29 @@
+Window < UIWindow
+  font: verdana-11px-antialised
+  size: 200 200
+  opacity: 1
+  color: white
+  text-offset: 0 4
+  text-align: top
+  image-source: /images/ui/window
+  image-border: 5
+  image-border-top: 22
+  opacity: 1
+  padding-top: 30
+  padding-left: 16
+  padding-right: 16
+  padding-bottom: 16
+
+  $disabled:
+    color: #aaaaaa88
+
+  $dragging:
+    opacity: 0.8
+
+HeadlessWindow < UIWindow
+  image-source: /images/ui/window_headless
+  image-border: 5
+  padding: 5
+
+MainWindow < Window
+  anchors.centerIn: parent