This commit should fix#225.
In order to avoid stalling LDAP connections, Authelia creates new
sessions for each set of queries bound to one authentication, i.e.,
one session for authentication, emails retrieval and groups
retrieval.
Before this commit, a failing query was preventing the session to
be closed (unbind was not called). Now, unbind is always called
whatever the outcome of the query.
I took the opportunity of this commit to refactor LDAP client in
order to prepare the work on users database stored in a file.
(#233)
A link to U2F explains what is a U2F security key and how they are used.
A tooltip on U2F device registration link is telling the user he needs a
security key to register.
The u2f-api package does not use the official u2f script provided by Yubikey.
Unfortunately, it was blocked by Firefox. This change reintroduces the
official u2f script.
