JinjaExpert - modify message fields using jinja2

[ghost]

This commit adds a simple jinja expert bot, that lets you modify message
data using jinja2 templates.
It add the relevant documentation to the bots file and also a couple of
unit tests.

[codecov-commenter]

Codecov Report

Merging #2040 (88f1084) into develop (c843349) will decrease coverage by 0.13%.
The diff coverage is 37.50%.

@@             Coverage Diff             @@
##           develop    #2040      +/-   ##
===========================================
- Coverage    76.07%   75.94%   -0.14%     
===========================================
  Files          425      429       +4     
  Lines        22824    23038     +214     
  Branches      3023     3067      +44     
===========================================
+ Hits         17364    17496     +132     
- Misses        4754     4835      +81     
- Partials       706      707       +1     

Impacted Files	Coverage Δ
intelmq/bots/experts/jinja/expert.py	37.50% <37.50%> (ø)
intelmq/bots/experts/tor_nodes/expert.py	46.42% <0.00%> (-2.33%)	⬇️
intelmq/bots/experts/asn_lookup/expert.py	35.83% <0.00%> (-1.89%)	⬇️
...telmq/bots/experts/recordedfuture_iprisk/expert.py	41.93% <0.00%> (-1.89%)	⬇️
intelmq/bots/experts/domain_suffix/expert.py	43.18% <0.00%> (-1.53%)	⬇️
intelmq/bots/experts/maxmind_geoip/expert.py	20.80% <0.00%> (-0.69%)	⬇️
intelmq/lib/harmonization.py	87.21% <0.00%> (-0.31%)	⬇️
...q/tests/bots/outputs/sql/test_output_postgresql.py	86.95% <0.00%> (-0.19%)	⬇️
intelmq/tests/lib/test_upgrades.py	100.00% <0.00%> (ø)
intelmq/tests/bots/outputs/smtp/test_output.py	100.00% <0.00%> (ø)
... and 14 more