Use better defaults for file paths and permissions

[bjoernricks]

What:

• /var/run is just a symlink to /run nowadays.
• Allow user and group to access to socket by default. This allows for querying data from osp in a multi-user setup more easily.
• Move pid file within /run/ospd
• There is no /usr/var directory by default. Therefore change the path to the certs to something that makes sense

Why:

How:

Checklist:

• [ ] Tests
• [x] CHANGELOG Entry

[codecov[bot]]

Codecov Report

Merging #429 (352d01e) into ospd-20.08 (4bfb08d) will not change coverage. The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           ospd-20.08     #429   +/-   ##
===========================================
  Coverage       74.35%   74.35%           
===========================================
  Files              23       23           
  Lines            2652     2652           
===========================================
  Hits             1972     1972           
  Misses            680      680           

Impacted Files	Coverage Δ
ospd/parser.py	88.63% <100.00%> (ø)

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