hourMin, hourMax and hourStep to give time blocks

I hope this is intelligible. 

I added three options,
hourMin, hourMax and hourStep for establishing time blocks within the day view.
useful for booking sytems where there are block of time.
![block_day](https://f.cloud.github.com/assets/496560/195165/c5b08406-7fdc-11e2-9268-288c0adedbd5.png)