Fix path to VexFlow target.
Add support for tracking VexFlow objects across component refreshes.
Upgrade Sencha framework versions.

The frameworks have all been updated using the recent Sencha Cmd release
3.1.2.342, and their latest versions are as follows:
 - ExtJS 4.2.1.883
 - Sencha Touch 2.2.1
 - Sencha IO 0.7.15
Add a shared "tutti" package.

The package is an empty skeleton for now, but with Sencha Cmd's support
for shared packages, we can move code out of the workspace classpath and
into individual packages to be included in the mobile and desktop apps.