We no longer need the install() function for installs that only set
the module version number. Same for upgrade(). Do a general cleanup
of all installers and remove the ones that are no longer necessary.
* Change $_POST to Input::instance()->post
* Explain what access::verify_csrf() does
* Avoid breakages on tag album pages (which don't have an item)
* Minor style fixes.
There's more that could be done here, but this is sufficient.