Swift content enhancements and fixes

I updated the swift content in the installation guide with a
few enhancements and fixes as follows:

1) Improved wording/phrasing (thanks Joe Robinson).
2) Improved consistency of duplicate content.
3) Added example output from ring builder commands.
4) Addressed other minor issues.

Change-Id: I14b6f07877677b3c1b38271150e7c39d19c2c96f
Partial-Bug: #1389382
backport: juno
Merge "Swift content enhancements and fixes"