More work on mouse interactions, and fix scissor clip rects being upside down

Mouse interaction working

- Update PIXI with some fixes for floating point textures ...

- Create the render buffer with format RGBA16F, because 32F doesn't seem to work for some reason
- Restore the proper ImGUI shader
- I fixed the PIXI types, so remove src/types/pixi.js.d.ts

More attempts at making render-to-texture work...

Use EXT_color_buffer_float to support blending from our render texture, using format=RGBA and type=FLOAT ...

Need to update PIXI to support RGBA32F (new build in pixi.js-504.tgz, needed to delete package-lock.json)
Still seeing problems with the framebuffer (it's complete, but no rendering?)

Fix flipped texture

Fixed the flickering rendering by making sure we properly save the gl state ...

Still need to fix the texture being upside down

Kind of have rendering working... every other frame

Plugin working, render texture not displaying

Doesn't seem to crash with fonts now, but can't find the renderer plugin?

Per-context IOs all over the place, but font loading is failing :(

Multi-contexts

More work on per-Sprite ImGui contexts (looks like we have different IO for every context, so make sure we set all of them)

Start working on a per-PIXI-DisplayObject context renderer for ImGui

Bring in the packaged UMD export of pixi.js from our own repo

imgui-js update (new .gitignore in imgui)

Moved the impl to the src/ folder so I can start working on a proper PIXI ImGui implementation (probably with render-to-texture)

Background color, start looking at better PIXI integration (need to be pixi-aware in imgui_impl)

Fix watch script (need to look at ./src) ...

Debug no mouse in ImGui :(

ImGui 'kind of' works in the PIXI renderer, but it seems scaled (DPI aware now???) and the mouse doesn't work

Start integrating ImGui into the pixi renderer

Fixed the imgui project so we can do a dev (incremental) build and a distribution build

Start prepping for dev SystemJS build

Test rendering some stuff finally!

Do all the building with the typescript rollup plugin (and ignore the cache folder for that). Include the node builtins plugin, and update imgui-js to fix the bad module references to imgui-js

Try using rollup with plain es2015 modules (commonjs for bind-imgui)

Try rollup (does it combine files?)

Very simple setup with systemjs. Doesn't load modules, doesn't rollup yet

Actually call init() on window load

Test index.html and main.ts file just to load up ImGui. May have to switch the module setup on imgui-js to not use systemjs, and go with something browserify-compatible