Fauxton: use .listenTo and not .on

There was no `.off` call on destroy, so these two Eventhandlers
where leaking memory
Fauxton: Extract a common filter component from logs

Create a reusable component from the filter that is used in logs,
that can be used in for tasks like
COUCHDB-2158 ("Apply filter with custom params on changes feed page")
and other situtations where a filter is needed.
Fauxton: fix regression for document editor

Introduced with ebade0f2f82d4da60e386f4aeaf24ecb98181e81
Use `os:timestamp/0 instead of `erlang:now/0`

We don't need the guarantees of `erlang:now/0` in `make_cookie_time/0`,
so `os:timestamp/0` is just fine.
Remove unused variable and function call

Finally get rid of that compiler warning.