Add troubleshooting for QueryError

[ci skip]
Update the caveats about authentication

[ci skip]
Add an example of how paging works

[ci skip]
Add a section about batches to the readme

[ci skip]
Add info about thread safety to the readme

[ci skip]
Update links that are used more than once to use footnote style linking

Also update the links to the CQL reference and Cassandra CQL docs

[ci skip]
Version bump to v2.0.0.pre0