Improve local proxy implementation

[occupant23]

Improvement

• [x] instead of trusting all servers it would be better to create a root certificate on the fly use the following approach: https://github.com/browserup/browserup-proxy/issues/137#issuecomment-535509225
  • add another property to decide which way should be used (Default: create a certificate on the fly)

Testing

• [x] add tests that verify the own code
  • [x] validate that the usage of properties leads to the correct behavior e.g. certificate are required
  • [x] validate that the RuntimeExceptions are thron correctly
  • [x] validate that the proxy is working (don't test the whole functionality) by using a basic function e.g. basic auth

Documentation

• [ ] add a new wiki page that describes the local proxy API
• [ ] use the page above to explain especially the basic auth via the local proxy
  • [ ] currently usage in Chrome is recommended since you are able to ignore certificate errors if you pass the following argument browserprofile.CHROMEPROFILENAME.arguments = -ignore-certificate-errors. FF is running but shows an SSL exception
• [ ] use and link the showcase https://github.com/Xceptance/neodymium-showcase/issues/13

[occupant23]

@oomelianchuk: Please review and test the implementation above.

[h-arlt]

Feature works as expected. Some small code improvements added as comments.

Q: In case the root CA cert file already exists, should Neodymium check if the cert is still valid? Q: Should the root CA cert file be automatically removed at VM exit? Q: Will the documentation tasks be handled in a separate issue?

[occupant23]

will do Q2, this solves Q1 automatically Q3 will be done within the release process

[occupant23]

documentation of the settings is done