Add own last pickup date to store info

What does this MR do?

Add own last pickup date to store info. Only get's displayed if there is a past pickup to help stores with pickup rules/limitations and to help foodsavers being fair/nice to eachother.

I think this small change helps users to be more considerate with their pickup quantity and to follow rules to make BIEBs life easier.

• Absolute date makes it easier to follow rules like (ones per calender-month)
• Date-count helps for situations like every 3 weeks.

How confident are you it won't break things if deployed?

Quite

Links

• Slack discussion: https://yunity.slack.com/archives/C1T1ZM9A4/p1558897065011400

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))