Add HTTP POST support to the HTTP client

[tomvanbraeckel]

I'm using this for of my (experimental, but working!) "find games" functionality, where one retro-go device connects to another's wifi hotspot and recursively "finds" (and downloads) ROMs that it doesn't have yet.

The idea is that kids can easily share games with each other this way, especially self-made GameBoy Color games as it looks like there will be a GBStudio workshop at Fri3d camp!

I'm thinking of giving the users a high-level choice of which ROM folders to check (/sd/roms/ or /sd/roms/gbc/ or /sd/roms/nes or /sd/roms/gb or /sd/roms/doom etc) to make it faster and more selective, in case there are many games.

Even better would be to to create a nice new "remote file browser" tab that properly allows you to browse another retro-go's (or in general. any webserver's) files. This could use the default http://192.168.4.1/ (assuming you're connected to another retro-go's wifi hotspot) but it would be nice to have some way of configuring this URL. So a method of entering an IP address or generic text on the retro-go would be cool... dream, dream, dream!