Adjusting regular expressions for features extraction

[tomchop]

Some changes to the regexes in features.yaml, mostly relaxing them:

• Removed the header check for sshd/pid, given that there were two versions: \[sshd, pid: \d+\] and \[sshd\] \[\d+\]
• Removed the .* at the start of some regexes which must've made them much slower.

[tomchop]

I sent it too soon because I'm working out of the same branch, but it should get decoupled as soon as the other one is merged. :)