This replaces the old set parser with a brand new one. This also changes
the internal algorithm from duplicating YAML to merging YAML, which
might solve a problem one user reported in chat, but which was never
captured in an issue.
Closes#1540Closes#1556
This removes the requirement that a fetch or install command must
explicitly state the version number to install. Instead, this goes to
the strategy used by OS package managers: Install the latest until told
to do otherwise.
Closes#1198