Change help documentation interface

[zph]

For flexibility, instead of USAGE: or SUMMARY: we could make the following interface:

1. USAGE is the first line after the #! that is not empty or empty after stripping leading comment chars
2. Full Description from USAGE (inclusive) until first line that is empty with no comment chars OR where it starts with non-comment char

Then the user can choose to use these strict patterns (usage:) for better interface but doesn't require as much control over design of the scripts.

[zph]

Closed via #10