Update mappings for MCP names in Forge update

Mapping updates corresponding to:

MinecraftForge@MinecraftForge/7c6468a9ea956e743e2e8c7314808525a65e6ebc
MinecraftForge/FML@1774e2bf3073c3449d1f289399971ad93a5b6479

Converted in and based on:

agaricusb/MinecraftRemapping@46f121acfd45b850ee760d1afa3aedc405df754a

Important Note: these mappings have argo and bouncycastle excluded, see:
https://github.com/MinecraftPortCentral/MCPC-Plus/commit/04ec475a7d77d801a33654564e5936119a53a618 Exclude argo from obfuscated mappings
https://github.com/MinecraftPortCentral/MCPC-Plus/commit/4989826eaeaf39cc11ca67f1491a58facb1260dc Exclude bouncycastle from obfuscated mappings

Also removed unused mapping files.
Update source for renamed MCP csvnames

https://raw.github.com/agaricusb/MinecraftRemapping/29d18b9299a04d7203c1afd3577c7d46d6e1ad2b/1.5.1/updatemcp-646-to-647.srg
grep -v egrep "func_|field_"
Update source for new MCP csvnames

https://github.com/agaricusb/MinecraftRemapping/blob/b340edda49add60fd138b445c251dfc004353ea5/quickupdatenames.py
Update to Forge 7.7.1.646

Completes the MCP mappings refresh