Laurence/update policies

Description

I've heard complaints recently that people did not know how to follow the policies of the project related to Gitlab. People found the policies to be difficult to consume, so this MR is an attempt to simplify them and make them more accessible.

Proposed changes

Changes proposed in this merge request:

• Updates old HACKING links to CONTRIBUTING
• Cleans up all of the links to be neat hyperlinks in markdown format , instead of full links
• Massively reduces amount of text relating to templates and also opening / closing tickets
• Removes information about nosoftware labels

Note: I have left in there what I believe to be some outdated info on the severity labels and impact labels since Tristan changed them. However I'm not too sure how there are actually being used at the moment, so would appreciate some input there. The new world order for severity labels really does not make sense to me....perhaps we can consider changing it back...but that's a discussion for elsewhere....

Also, I think we may need to outline better how to flag a bug you are raising as 'high priority' so that the development team take a look at it.

Admittedly, some of the finer details have been removed. But I believe it is worth it in order to have a more accessible and easy to digest policy.

Gitlab issue this MR closes

No related issue - apologies, I forgot to raise an issue and just went straight into writing the patch.