Add recurring task

[huytd]

Recurring task is something pretty useful.

Especially in my case, I had to pay a lot of bills every month, but hates to setup automatically payment. There's nothing worse than having money going out of your bank unconsciously.

Proposal syntax:

COMMAND ?DATE ?TIME REPEAT TAG TITLE

COMMAND = rt | rtask | retask | recur | recurring
DATE    = DD-MM-YYYY | YYYY-MM-DD | MM/DD | MM-DD | <null>
TIME    = HH:mm:ss | HH:mm | <null>
REPEAT  = DAY | HOUR | MONTH | YEAR
DAY     = [number]d
MONTH   = [number]mo
YEAR    = [number]y
HOUR    = [hour]:[minutes] | [number]h | [number]m

With any of the DATE and TIME as null, we'll use the current date and time.

Example:

  rt 2019-05-01 15:30 5d @tag task description here
  rt 30m @tag task description here
  rtask 10/15 30m @tag task description here
  rtask 10-15 5d @tag task description here
  recur 2d @tag task description here
  recur 15m @tag task description here