"content-centric" format of remote list output, instead of table

[preminger]

Much of the output generate by singularity remote & its subcommands involves tables populated by YES/NO values. This is a visually "busy" output & not the most useful.

Since the overwhelming majority of cells in these tables end up being populated by "NO", this table-oriented output format should be scrapped in favor of a list of entries, in which - if the particular entry has any fields that would have been set to "YES" - that field is simply spelled out in the parentheses. Example:

$ singularity remote list

Cloud Services Endpoints
========================
SylabsCloud (cloud.sylabs.io; active, global)
company-remote (enterprise.example.com; global)
myremote (enterprise.example.com)

Keyservers
==========
1. https://keys.sylabs.io (global, active)

Discussion: #1639