extend user agent filter by "python", "wget" and "monitor"

[stklcode]

Fixes #149

Back in #125 the user agent filter for bot detection has been reworked.
As @KittMedia already mentioned in #125 (comment) the wget identifier has been forgotten while curl is present. Never taken care of that...

Also commonly used monitoring tools like Nagios/Icinga or PRTG are not excluded. They are not "bots" in terms of crawlers/spiders, but also non-human requests which are not meant to be counted. Both contain the word "monitor(ing)" while afaik no client webbrowser contains this.

I've also added python, because it's quite common for analysis scripts and bots as well.

Example UA strings that pass the 1.7 filter, but shouldn't:

Wget/1.20.3 (linux-gnu)
Python-urllib/3.8
python-requests/2.22.0
check_http/v2.2 (monitoring-plugins 2.2)
Mozilla/5.0 (compatible; PRTG Network Monitor (www.paessler.com); Windows)

The latter also passed the <=1.6 filter, because it contains "Windows"...

[patrickrobrecht]

LGTM.