distinct URI for suspend/delete

/users/?suspend=<username>  =>  /users/suspend/<username>
/users/?delete=<username>   =>  /users/delete/<username>
added possibility to delete users
added granting/revoking of admin privileges

any admin (username 'admin' or account_type 'admin') can toggle the
account_type of any other non-guest user from 'admin' to 'user' and vice-versa
the "real" admin (username 'admin') is of course unaffected
Merge branch 'master' into usermgmt
Merge branch 'master' into usermgmt
Merge branch 'master' into usermgmt
Merge branch 'master' into usermgmt
Merge branch 'master' into usermgmt
Update sagenb/notebook/notebook.py

Add Fricas as one of the SYSTEMS options.
Make pyOpenSSL an optional dependency

See Sage trac #13385: http://trac.sagemath.org/sage_trac/ticket/13385

Basically we want to fail gracefully if pyOpenSSL isn't installed. This
commit preemptively turns off secure mode as soon as notebook() is
called if it detects pyOpenSSL is not installed. There is also a single
OpenSSL import in sagenb's own code, so I wrapped that as well just in
case.
Don't silently turn off HTTPS

Actually, rather than falling back to HTTP when HTTPS cannot be used, we
should just throw an exception. Otherwise, users may be misled into
thinking they are using HTTPS when they are in fact not.
Merge branch 'master' into usermgmt
Update SSL information in the README
Merge pull request #95 from kini/wrap-ssl-import

Make pyOpenSSL an optional dependency
Version bump to 0.10.2
Merge branch 'master' into usermgmt
With introspection and live documentation in the notebook, fix spurious \(,\) and \[,\] pairs
Fix introspection and live documentation in the notebook
mmarco's idea to solve "invalid username" error

Trac 13536 - password recovery does not work.
This is mmarco's patch for fixing it.
create default users if "admin" doesn't exist