Bug 182: exclude some transaction types from total funding

[rajeshg]

Description

Changed query to calculate Total funding. We now exclude Interest and substract the refund amount. Closes https://github.com/ncopenpass/CampaignFinance/issues/182

Why?

The Total Funding Field on the candidate page is calculated without accounting for transaction types. For example, it counts refunds and individual contributions. From what I can tell, this is not the behavior we want.

GitHub Issue

https://github.com/ncopenpass/CampaignFinance/issues/182

Testing Steps

Before and After Screenshots (if applicable)

[rajeshg]

@SchaeStewart can you review this?