When a YAML/TOML's delimiter character sequence is included in a
frontmatter string, parser mistakes it as a delimiter. This fixes it by
checking a character right before the delimiter sequence is '\n' or it
is the beginning of the frontmatter.
Fix#1320
This rewrites `extractFrontMatterDelims` function to make it work with
an archetype file without the final EOL and adds more detailed error
messages and comments.
It also removes `matches` and `matches_quick` functions which aren't
called anywhere.
As pages are read from the target, they will be assessed if they should
be rendered or not. The logic for IsRenderable is in the parser/page.go
and looks for anything exception '<'.
