modified include to search from the project root (as iverilog does) in addition to relative to the source file directory

one of the editor windows instead of the file if it is open (possibly
dirty)

mark it as an error

* Homebrew installs vvp and gtkwave on /usr/local/bin, so current tool
* file failed because the path was not including this folder. Easier to
* add a config and allow custom vvp/gtkwave location.