core: for websocket, set a minimal reqdata with peer and port nr.
core: serialize {term, 'undefined'} as sql null value.
core: Opcode and encode_as_binary addtion to ubf api.
doc: Changed observer to observe.
Extended docs for URL controllers with example rendering a template.

Needless to say, feel free to refuse the PR if you think it is the wrong place or inadequate.
doc: Fixed name of module's template directory.
doc: Update custompivots.rst
mod_menu: Fix add menu item

Fixes #744