Visualize using multiple Filter Expressions

[fxnn]

As a user, I want to plot the summarized transaction amounts for multiple filter expressions in one chart, so that I can get a focused and aggregated report on the spendings that currently concern me.

Requires: #7

• Allow for multiple filter expressions
• For every filter expression, add a series to the chart
• Add optional "remainder" series, showing the sum of unfiltered transactions' amounts