cjdns: new declarative service expression

systemd service wants network-interfaces.target rather than network.target
assertion on config.networking.enableIPv6

(cherry picked from commit f60ac82cac0c4c94da76d294114955c8185752ff)
cjdns: package update from 20140303 to 20140829

(cherry picked from commit fc6ccd1080918a433d03f9e0762296b0e486aef8)
cjdns: update 20140829 to 20140919

Closes #4186

(cherry picked from commit 95c72a5f6056a5be64f627112d72ea39e9e85715)
cjdns: update from 20140919 20140922

package installs to .../bin
fix service module to look in .../bin

Closes #4240

(cherry picked from commit 61f0d9b251fd0dda6dfb263a43f6ccb5e0c9aa97)