Hyperlinks resources generation adapted to Jenkins 1.458.

Previously all static resources were broken because of
the different mechanism used by Jenkins to allocate
static URL to resources.

See: 
https://wiki.jenkins-ci.org/display/JENKINS/Hyperlinks+in+HTML
Icons size adjustment and padding.
Stabilisation and simplification of the Assembla ticket regex.

A default value is now provided in order to simplify
the first-time configuration.
No specific restrictions anymore on the regex groups,
just define any regex and the ticket number will be
automatically fetched as the first number sequence in 
the recognised group.

Default regex: \[#[0-9]+\]

Sample commit: [#256] NPE workarounded
-> Associates the Build to the Assembla Ticket #256