Add vendors

[matt-benton]

I want to be able to add vendors and attach them to expenses. This would allow me to pull up a page for vendors that shows information such as how many times I bought from that vendor, how much did I spend there on average, how much did I spend overall, how much did I spend in the last 3 months, etc.

[matt-benton]

Divide these queries up into increments such as previous 3 months, last year, this month, etc.