Throughout the product, we've always hard-coded the product name as

"Review Board", which we then had to override in RBCommons, often

resulting in a mix of names. Sometimes this is appropriate (as we're not

hiding that the product is Review Board underneath), but often it is

not and can end up being a bit confusing.
This adds a new settings.PRODUCT_NAME constant that we can use

throughout the product. It's defined as "Review Board" here, but we'll

be able to override that with "RBCommons" and reduce the number of

templates and other code paths we have to override, making future merges

easier.

Tested all affected pages with and without a custom product name.
Unit tests pass.