Add many new commands and bug fixes

New features

• [commands] Add the following Hash COMMANDS: HDEL, HEXISTS, HGET, HGETALL, HKEYS, HLEN, HMGET, HSET, HSTRLEN, HVALS
• [commands] Add the following List COMMANDS: LPUSH, LRANGE, LREM, LSET, LTRIM, RPOP, RPOPLPUSH
• [commands] Add the following String COMMANDS: APPEND, MSET, MGET, STRLEN
• [client] Add --commands to view the list of all commands
• [client] Add --encrypt and --decrypt options to encrypt/decrypt data using a GPG keypair
• [client] Add -- option to read last argument data from STDIN

Bug fixes

• Ensure listening on a socket will abort after *KV_abort seconds
• Reading frorm a socket shouldn't return "no data" or "unknown data" if there's no data. It should just print an empty string.
• Errors should throw/raise an error with the message, for the client to parse
• Perform more validations on individual commands, ex: ensuring a Key is a list, etc
• Temporarily disabled integrations tests because they cause false/positives

Misc changes

• Change the way IDENT and AUTH is performed in client and server
• Client doesn't print "OK " anymore for every command
• Simplify much of the kv command processing code