General purpose reformating and rewording in (a few places). This should
also make markdown linting happier.
Prefer back-ticks wherever useful and use `console` for code blocks to
be executed on terminal.
Also, update references links wherever possible (including update from
'http://' to 'https://').
- Add missing documentation for options and environment variables
- Rearrange definition and documentation of 'Options', 'Variables'
and 'Aliases' in a consistent order
Entries from static '/etc/hosts' can now be ignored via 'zstyle' based
configuration. Both IP address and corresponding hostname will be ignored
during host completion. However, some of the entries ignored from '/etc/hosts'
still might appear during completion because of their presence in 'ssh'
configuration ('~/.ssh/config') or history ('~/.ssh/ssh_hosts',
'~/.ssh/known_hosts' etc.).
