Add Date format finder support and other date support

[pateash]

reference - https://nsdateformatter.com/

command should be able to give POSIX date format for a given date

[pateash]

https://www.ibm.com/support/knowledgecenter/en/SSLVMB_23.0.0/spss/base/syn_date_and_time_date_time_formats.html

[pateash]

https://momentjs.com/

[pateash]

• format date with a given format
• use relative feature from momentjs
• use timezone locale feature for converting date from one to another

[pateash]

cdt date -d "20190311" -> should provide date and its format