Downloads handled by bridge instead of mod

[WhiteHusky]

• [x] Bridge portion
• [x] Mod portion

Instead of having the mod receive the bytes directly, have the bridge place the files itself for the mod to find and move around into place as needed.

Also miscellaneous refactors.

Security considerations: The mod can tell the bridge to place the files anywhere, but the bridge will not overwrite files nor try to delete file paths it didn't create.

[WhiteHusky]

@AsciiJakob aka Verb reports the following numbers for a 233MB download on a 1Gbps connection. Game has the default limit framerate option (30FPS) when unfocused

Patch	Condition	Total Time
0.4.5	Focused	99s
0.4.5	Unfocused	499s-501s
PR	Focused	28-31s
PR	Unfocused	27-29s

[WhiteHusky]

Fixed build issue; I had some changes that I'll wait for another PR for and selectively staged but kept back too much.

[WhiteHusky]

This will fix #102 as an aside.

[WhiteHusky]

May have forgotten to account for mods that updated. Additionally might need to change how mods are saved to avoid two mods of the same name from two servers clashing together (sha256 sum?)