Better develop the function For nodejs

add `export.includeExtFunc` and `export.parseMethodExtFunc` Interface

1. includeExtFunc: Use it when `parse` meet `include`
2. parseMethodExtFunc: Expand methods by using the string between "<%" and "%>", 

For Example:
https://github.com/Bacra/node-d2server/blob/dev/lib/parser/htmlTpl.js