I fixed typos and grammar + rephrased some things that didn't seem to flow
The only major change is the section on PSQL_PAGER.
In the section on the new --create-slot option for pg_basebackup, it seems like <option>--slot</option> should include the =slotname part but I don't know the DocBook markup for that (maybe <replaceable>?).
I did not build the documentation after making my changes so the patch definitely needs to be sanity checked.
