Improve Ignore mode and the blacklist

Improve Ignore mode and the blacklist

When you reloaded the page or visited some other page in the same time while in
Ignore mode, you'd always end up in Normal mode (unless the newly loaded page
was blacklisted). Now, you stay in Ignore mode in that case. This lets you press
`i` and browse around in that tab in Ignore mode, without having to press `i`
again any time a full page reload is caused.

However, if Ignore mode was entered automatically because of the blacklist, it
is also exited as expected if you browse to a non-blacklisted page.

This new behavior is possible by tracking the "type" of the Ignore mode. There
are currently two types, 'explicit' and 'blacklist', which correspond to the
above two cases.