Build 2944 - Raspberry Pi and VS Code Debugging

Build 2944 adds some new goodies - it's finally running smoothly on a Raspberry Pi3B (make sure you've got the GL driver enabled), and much better integration into Visual Studio Code (or code-oss if you're on a PI)

• First Raspberry Pi preview release - currently only tested on a Pi3B.  Needs the full versions of Raspbian Stretch or Buster, may not work on "lite" versions.
   
• Far better VS Code integration - if you're launching from the Itch app, you can click the "VS Code Workspace" button to launch VS Code with a ready built workspace.  Debugger support is also WIP - install the Duktape debugger plugin (which should get auto suggested by the workspace), run Prism, and do IO.debug("myfile") and select Debug -> Start Debugging in VS Code.   Breakpoints may or may not work, depending on platform!
   
• Added new 'Welcome' screen on startup - this will eventually have tips, and options for quickly launching things
   
• Lots of fixes and improvements to the built in Help viewer
   
• Reorganised the default tile graphics set, into a 4x4 page layout - individual pages can be loaded in without loading the whole image.
   
• Performance improvements in graphics renderer
   
• Working towards getting an Android build working (it currently fails to initialise the graphics properly, so exists on startup)