Tracking issue: advanced search features

[grunweg]

Let's collect all ideas for "more advanced search" here:

• by author: author:grunweg etc. - implemented with a small hack #...

• by assignee: assignee:grunweg etc. - unimplemented; would be easy to add

• labels, with the t-algebra$ tweak - implemented with a small hack

• Disable searching in the description (Search/filtering that also searches through PR descriptions #79)? I guess that is not necessary; providing more localised ways of searching certain fields seems more useful. The only one remaining could be the PR title.

• search for a list of authors (Filter for PRs by a user-set list of users #72): authors:grunweg,jcommelin finds all PRs by grunweg or jcommelin

• logical operators: OR and NOT (Logic operators in search box #84)