This PR adds three new hash commands: HGETDEL, HGETEX and HSETEX. These
commands enable user to do multiple operations in one step atomically
e.g. set a hash field and update its TTL with a single command.
Previously, it was only possible to do it by calling hset and hexpire
commands subsequently.

- **HGETDEL command**

  ```
  HGETDEL <key> FIELDS <numfields> field [field ...]
  ```
  
  **Description**  
  Get and delete the value of one or more fields of a given hash key
  
  **Reply**  
Array reply: list of the value associated with each field or nil if the
field doesn’t exist.

- **HGETEX command**

  ```
   HGETEX <key>  
[EX seconds | PX milliseconds | EXAT unix-time-seconds | PXAT
unix-time-milliseconds | PERSIST]
     FIELDS <numfields> field [field ...]
  ```

  **Description**
Get the value of one or more fields of a given hash key, and optionally
set their expiration

  **Options:**
  EX seconds: Set the specified expiration time, in seconds.
  PX milliseconds: Set the specified expiration time, in milliseconds.
EXAT timestamp-seconds: Set the specified Unix time at which the field
will expire, in seconds.
PXAT timestamp-milliseconds: Set the specified Unix time at which the
field will expire, in milliseconds.
  PERSIST: Remove the time to live associated with the field.

  **Reply** 
Array reply: list of the value associated with each field or nil if the
field doesn’t exist.

- **HSETEX command**

  ```
  HSETEX <key>
     [FNX | FXX]
[EX seconds | PX milliseconds | EXAT unix-time-seconds | PXAT
unix-time-milliseconds | KEEPTTL]
     FIELDS <numfields> field value [field value...]
  ```
  **Description**
Set the value of one or more fields of a given hash key, and optionally
set their expiration

  **Options:**
  FNX: Only set the fields if all do not already exist.
  FXX: Only set the fields if all already exist.

  EX seconds: Set the specified expiration time, in seconds.
  PX milliseconds: Set the specified expiration time, in milliseconds.
EXAT timestamp-seconds: Set the specified Unix time at which the field
will expire, in seconds.
PXAT timestamp-milliseconds: Set the specified Unix time at which the
field will expire, in milliseconds.
  KEEPTTL: Retain the time to live associated with the field.

  
Note: If no option is provided, any associated expiration time will be
discarded similar to how SET command behaves.

  **Reply**
  Integer reply: 0 if no fields were set
  Integer reply: 1 if all the fields were set