CLI - Date/Time

Working on the CLI. Implemented date/time options:

• doe Calculate date of Easter, for a given year.
• cd_to_dn Convert civil date to day number.
• gd_to_jd Convert Greenwich date to Julian date.
• jd_to_gd Convert Julian date to Greenwich date.
• ct_to_dh Convert civil time to decimal hours.
• dh_to_ct Convert decimal hours to civil time.
• lct_to_ut Convert local civil time to universal time.
• ut_to_lct Convert universal time to local civil time.
• ut_to_gst Convert universal time to Greenwich sidereal time.
• gst_to_ut Convert Greenwich sidereal time to universal time.
• gst_to_lst Convert Greenwich sidereal time to local sidereal time.
• lst_to_gst Convert local sidereal time to Greenwich sidereal time.