added two new contract methods to the caller class, load_data and expected_callbackargs (static)
this means that the base class is the only place that needs a constructor
and that no data loading happens in the constructor
this in turn means we can check callback argument validity much more lightly
also completely remoted portfolio_add_button function and replaced with a class
as the argument list was getting out of control. it's now much more readable.
this introduces portfolio/file.php to serve portfolio related files - access check is delegated to the plugin.
and also two new classes in the portfolio plugin tree - push vs pull.
Not done:
- forum (the rest of the module isn't using files api yet)
- database mod (touches other parts of the code (ods and excel libs)
- portfolio download plugin (needs discussion with petr about userfiles)
all of these have been disabled in the meantime.
