Added a gui to make custom filter

I moved the JavaScript and css into separate files.  Then I implemented a simple input box that allows a user to make filters by the gui.

This is the first time I contribute to an open source project (other than mines).  So I do not not know how far can I go into changing the code.  I tried to respect as much as I could the current code style.

I did not take the liberty to add unit tests to the javascript.  If welcomed, I would like to use qunitjs as the unit test framework.

cheers!

didier