Small fixes for scaffold post-type

1. The escaped quotes were not needed anymore with the mustache template and caused the parsing of wrong urls when editing, saving or publishing a post.

2. Default query_var value was set to the slug and without settings the slug parameter it caused notices on the frontend when viewing a post. Changed it by default to true. This is in line with the codex: http://codex.wordpress.org/Function_Reference/register_post_type