shell: Change default byte suffix to KB

Instead of using the more geeky KiB and such suffixes, use
KB consistently. Try to use 1024 factor as much as possible
for consistency.

Fixes #704
shell: Move cockpit_format_bytes into cockpit namespace

And make the function easier to use correctly
shell: Put cockpit-storage code in own private scope
shell: Move the cockpit_format_bytes_long into storage code

This is where it's used from and it's storage specific.
shell: Move cockpit.format_bytes_per_sec into cockpit scope
shell: Move cockpit.format_delay into cockpit scope
shell: Remove unused cockpit_add_thousands_separater function
shell: Move cockpit_format_temperature into storage code

It's currently disk specific, and so scope it appropriately.
shell: bits rather than bytes to describe network throughput

Refactor how we build up the suffixes.

Fixes #855
Closes #877