Sanitize percent signs in help messages

[DannyBen]

This PR makes it so % symbols in help messages do not cause an implosion.

Before this PR, the following YAML failed.

name: cli

args:
- name: factor
  help: Provide % of change
- name: template
  help: Any string. Use %h or %H to specofy hostname

and the only way to make it work prior to this PR was to use %% instead of % - which then broke other uses of the string, such as generating man pages.