Improved PDF export and made LDAP compatible to anonymous bind

In this commit, I modified the raw base version 2.1.8 of TeamPass with
the following changes:
- add PDF encryption (requires password)
- add password input field for PDF export
- add folder tree to PDF table headers
- repeat table headers on every folder change in PDFs
- add monospace font for passwords in PDFs
- log PDF exports (who, when, which folders)
- in views, add page to view these logged items
- automatically set focus to search field when opening search page
- use PHP's built-in LDAP class instead of AdLDAP because the latter
apparently doesn't support authentication via "anonymous bind" method
(first bind anonymously and ask for DN using username, then bind again
with retrieved DN and authenticate) and without anonymous bind, it
didn't work with our OpenLDAP