Added expiration support and other options support for SET and delete support

[generalpy101]

Check https://redis.io/commands/del/ for DEL command.

The SET command supports a set of options that modify its behavior:

EX seconds -- Set the specified expire time, in seconds.
PX milliseconds -- Set the specified expire time, in milliseconds.
EXAT timestamp-seconds -- Set the specified Unix time at which the key will expire, in seconds.
PXAT timestamp-milliseconds -- Set the specified Unix time at which the key will expire, in milliseconds.
NX -- Only set the key if it does not already exist.
XX -- Only set the key if it already exists.
KEEPTTL -- Retain the time to live associated with the key.
GET -- Return the old string stored at key, or nil if key did not exist. An error is returned and SET aborted if the value stored at key is not a string.