Improve Summary Graph

Currently the graph in the Summary tab is not bad if you have a lot of data, but for beginning who don't have a lot of data, it isn't as useful as it could be. A quick solution is to just make every day a data point. However this does not look good for users with lots of data, as it isn't as smooth as it could be.

1) The graph should always display some visually useful/sensible. Basically, I think we need a function that says, give me X data points. So if we request 10 data points and the user only has two days of transactions, the first five are the first day and the second five are the second day. 10 days of transactions would yield each as a data point, and 200 days of transactions would yield each 20 day group averaged as 10 averages.

2) Show a legend such as "Balance" and "Trend", so the user better understands the two lines.

3) Make the axis "ticks" more useful, by custom doing the strings. The Y ticks should be money strings and the X ticks should be dates.

4) The last data point on the Balance line should always be the total balance, and at the current date (today).

5) Add SpinCtrl's for adjusting the granularity (number of points) and the degree of the best fit curve, which change the graph as they are changed.