Chart should handle itself the fonction tree

[bleucitron]

Currently, <Chart /> only accept an array of values and this array is updated when a click occur on a <Bar />, which via the handleClick callback (part of each value) selects a different fonction.

This pattern is not very intuitive.

<Chart /> should be able to handle itself the selection of the different fonctions.

• it should be passed the aggregated fonction tree
• the fonction selection is internal
• a custom event should be dispatched to inform the parent that a fonction has been selected

It is probable that most of budget, code, fonction and tree stores will be useless after that.

• [x] refactor Chart as described
• [x] rename Chart as BudgetHisto
• [ ] audit stores and remove useless (this fixes #138)

[bleucitron]

In the end, it's much easier to have the Summary handle the tree via stores.