p12n: add script to save p12n info in json format, view to display searchplugins and protocol handlers

I've been using the Python script for about 6 months to generate views on searchplugins (http://l10n.mozilla-community.org/~flod/p12n/), only had to fix a couple of problems with Seamonkey productization.

It generates two files:
* p12n/searchplugins.json contains all p12n info
* p12n/index.html is a file used to check errors on all products/branches. It's useful for l10n-drivers, not for users, that's why is not explicitly linked anywhere

Partly fixes issue #30 (no error check at the moment).