Introducing headers to the .v files

[whisky-jb]

After my first pull-request was approved, I'm getting into v more and more. What I noticed (and I hate it ;-) is the fact, that all the files miss proper documentation. So what is file xyz.v doing? Should we start introducing a common header where we put some thoughts on the file purpose?

Something like this?

/******************************************************************************
**
** parser.v
**
** Main parser file, gets called after lexer and produces an AST structure.
**
*******************************************************************************/

That is obviously an example but when I dig into something, having a template header would help me to also do a standardized documentation and it will help other to understand more on the v source code.