Set position: relative to the container if position: static

[maxkfranz]

This makes it easier for extension writers to absolutely position elements within the Cytoscape div.

The position is set using an inline stylesheet prepended to the document head. It uses the __________cytoscape_container class to try to avoid collisions with user-set classes. In this way, properties set in the style attribute still take effect and most selectors in the user's stylesheet would allow for overriding the inline stylesheet.

A message with a stacktrace is printed to the console if somehow the div ends up being position: static.