Any projects which want to use Hush code from now on will need to be licensed as
GPLv3 or we will send the lawyers: https://www.softwarefreedom.org/
Notably, Komodo (KMD) is licensed as GPLv2 and is no longer compatible to receive
code changes, without causing legal issues. MIT projects, such as Zcash, also cannot pull
in changes from the Hush Full Node without permission from The Hush Developers,
which may in some circumstances grant an MIT license on a case-by-case basis.
Added AsyncRPCQueue::closeAndWait() so rpcserver can block on worker threads when shutting down.
AsyncRPCOperation is no longer copyable - copy constructor and assignment operators now private.
Refactoring: renamed methods, renamed member variables
Tidy up: comments, const, size_t, braces
