Add browser history runner

Being a DBus runner inside p-b-i has the obvious disadvantage of only working when the browser is running but I have it open all the time anyway.

It is added as an optional permission as to not cause prompts after upgrading the extension. Instead, it asks the user to grant the permission either on settings screen or in KRunner results.

Results are primarily scored by whether the title contains (starts with rated higher), host contains (+ starts with), path contains (+ starts with) in the same way as is done in tabs runner, except that the base score is slightly lower. Additionally, the number of visits to the pages (visited by opening the page, and visited by explicitly typing into the address bar, the latter of which is scored higher) is taken into account relative to the result set for added accuracy.

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@fvogt @davidedmundson @alex @vkrause @ngraham

Depends on: frameworks/krunner!48 (merged) (need to agree on a pixel format)

It complements the tab runner in a way that history runner does not return pages that are currently open to avoid duplicates.

Can deal with multiple browsers at once. Here Chrome has it enabled, Firefox lacks permission. The "additional permissions requred" entry has the lowest possible priority so it will only show if there few results overall so it's not as invasive.

Unfortunately, Firefox provides no way to get favicons for bookmarks.

Clicking on the "permissions needed" entry opens a page to request access which also explains how to disable this feature altogether when not wanted. Some design help needed here, of course :)

Settings page now has two runner settings grouped under the same heading: