Added possibility to enter past date in /spend command to log time in the past

Open username-removed-238711 requested to merge smcgivern/gitlab-ee:1312-time-spent-at into master

What does this MR do?

Provides feature to enter date in /spend command to logging time in the past. In UI there was added date when time was spent like on a screenshot. Example: '/spend 10m 2017-02-02'. Acceptable formats of date: long: YYYY-MM-DD, short: YY-M-D or mixes of this. Acceptable delimiters: '-' '/' '.' and few variants of delimiters mixes but i highly not recommend this


Issue #1312

Edited by username-removed-238711