Reduce duplication, provide clearer learning path in documentation

[petersilva]

Manual review required. I think there is considerable redundancy/room for confusion in that, for example, the following
three documents cover the same ground, all differently... wondering if there is room for rationalization:

https://metpx.github.io/sarracenia/Tutorials/1_CLI_introduction.html
https://metpx.github.io/sarracenia/How2Guides/subscriber.html
https://metpx.github.io/sarracenia/Tutorials/Setup_a_local_subscriber.html
https://metpx.github.io/sarracenia/Tutorials/Setup_a_remote_subscriber.html
Hmm...

Also there are sr3-examples now... It might be good to have a "Start Here" kind of guide to provide a little more guidance for people starting?