Cleanup Essex_Hog, update authentication docs

[valentijnscholten]

To authenticate to Confluence Server or Datacenter using a PAT (Personal Access Token) (Bearer token), it should NOT be base64 encoded.

See https://confluence.atlassian.com/enterprise/using-personal-access-tokens-1026032365.html

This was already working for JIRA/Gottingenhog, but not yet for Confluence/Essexhog.

I also made sure all variables in EssexHog are named confluencexxxx to avoid any confusion with GottingenHog.

Ideally the authentication is extracted into a shared piece of code ("atlassian auth"), but since this is my first Rust code change ever, I didn't dare to go that way :-)

Updated docs a little bit as well to help people deciphering the differences between Cloud and Server/Datacenter authentication which are handling the PATs differently.

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[valentijnscholten]

Looks like the base64 fix was already added a long time ago. I missed that as I was looking at the source of the latest release v1.0.11 which does not contain that fix yet. Time for a new release?

[cutler-scott-newrelic]

Hi @valentijnscholten , I can work on a release this week, but without Github actions I don't think I'll be able to produce many binaries other than what I can make on my own work laptop. As for this PR, thanks for the work and cleanup, much appreciated. Is this PR still valid and synced with the latest changes in master? If so I can merge it before issuing the release. (My only problem is that I may not be able to test it on my employer's confluence server.)

[valentijnscholten]

Yes it's up-to-date and contains no code changes, just naming and docs.

[valentijnscholten]

Looks like previous releases were done manually as well via [build_ghrelease.sh](https://github.com/newrelic/rusty-hog/blob/master/build_ghrelease.sh)