Fixed three typos that were causing errors after a rebuild.
Added a template helper that grabs a type by index of a parameter pack.
All Server requests are now more aptly named!
The Server requests are now better parsed in rpc.cpp.

It seems to be working fine!
All Server requests now generate a response when applicable.

With this commit: Request types now store the result of the operation in
a member struct, in addition to implementing a function that uses the
information in that struct to generate a single json value that is
either the result or the error returned to the plugin client.