ToscaWidgets 0.9.8 bugfix for tw.dynforms

[Alessandro Molina]

I don't know if it has been already fixed, but as it isn't available on
http://toscawidgets.org/hg/ToscaWidgets/ probably it is not.

As I reported to Chris there is a little bug in Tw0.9.8 caused by the merge of
this commit: http://toscawidgets.org/hg/ToscaWidgets/rev/e1e802e5e6b5 that
broke tw.dynforms HidingComponentMixin which uses tw.api.encode which has been
removed.

Patch is quite simple and I made it available here:
http://bitbucket.org/_amol_/toscawidgets/ feel free to pull from there if
needed.

As Chris stated probably a Singleton would be a better solution to the
problem, but in the mean time that unbreaks tw.dynform. As Chris is probably
quite busy I sent this email here so that there is trace of the fix and anyone
can merge it.

Alessandro