Ban all Diffie-Hellman ciphers in Java 1.7.0_6 and higher

Addresses an issue in SSL/TLS/GSI sessions that approximately one
out of 256 connections fail with an 'invalid padding' error. This
affects gridftp, webdav with https, httpd with https, SRM and gsidcap.
It should be noted that this significantly reduces the number of
available ciphers.

It appears that Diffie-Hellman is broken in Java 1.7.0_6 and higher. This
patch bans those ciphers if a broken version of Java is used.

The patch adds new configuration properties for configuring whether
certain cipher families are banned:

dcache.security.ciphers
webdav.security.ciphers
httpd.security.ciphers
gsidcap.security.ciphers
srm.security.ciphers
gridftp.security.ciphers

The latter are defined in terms of the first. The property names follow
the schema agreed upon at the 2013 developers workshop. The patch
introduces a new configuration property group called security. It is
intended for general security related properties like authentication,
authorization, cryptography, etc.

Target: trunk
Request: 2.6
Request: 2.2-sha2
Require-notes: yes
Require-book: no
Acked-by: Dmitry Litvintsev <litvinse@gnal.gov>
Patch: http://rb.dcache.org/r/5616/
Merge pull request #94 from gbehrmann/fix/2.2-sha2/rb5616

Ban all Diffie-Hellman ciphers in Java 1.7.0_6 and higher