OpenVPN:Add HMAC, cipher 'n2n' and DH key selection. Fixes and new design.

Added HMAC algorithm selection menu for N2N and RW.
Added cipher selection menu for N2N connections.
Added DH key selection also for existing installations incl. DH key upload possibility.
Adjusted the ovpn main WUI design to IPSec WUI.
Extend key lenght for CA, cert and control channel with faktor 2.
Some code and typo cleanup.
Bugfixes for #10317, #10149, #10462, #10463
V.2 New changes:
Integrated changes in langs and ovpnmain.cgi until 20.03.2014 2.15-Beta3.
ovpn.cnf have now default bits of 2048 instead of 1024.
ovpn.cnf default_md works now with sha256 instead of md5.
Bugfix: By new installation the auth directive for RWs is faded out #10462 Comment 15.
Added error message if the crl should be displayed but no crl is present.
Merge remote-tracking branch 'ummeegge/openvpn' into next