Fix search-whole-site vs section-only bug.
Remove unneeded arrows to children, completely rewrite fake arrows

When there's only 1 reply, the layout becomes flat and no arrow is
needed. Rewrite the PNG arrow code and layout algorithm and CSS to
fix this.
Tweak CSS: Increase distance after block with flat layout

And paint white background below "Reply" button.
Tweak CSS: Place thread resize handle in the middle.
Hide collapse-thread marks, they're so ugly

Also adjust margin-left for a folded thread, and add more space below it.
Update debiki-dao-pgsql.
Rename module debiki-dao-pgsql to debiki-dao-rdb.
Move E2E classes to packages test.e2e.code and test.e2e.specs

Also move-rename ChromeSuiteMixin to StartServerAndChromeDriverFactory and
separate file.
Make path to Chrome Driver configurable

And use a newer driver — the old one is no longer able to start the
E2E tests at all, Chrome just shows an empty page forever.
Use a more recent Selenium driver, so E2E tests work with FireFox.
Change Chrome driver path config value name.
Make methods private.
Add action CloseTree.
Tweak CSS: Place column separator close to left thread again

It feels annoyingly easy to accidentally click-&-drag it if it's in the middle.
Fix too-many-horizontal arrows bug.
Reformat sortPostsDescFitness(posts).
Sort new posts before old ones.
Re-add modules/debiki-dao-pgsql, so can be properly deleted.
Delete modules/debiki-dao-rdb, re-add later.
Properly delete modules/debiki-dao-pgsql.