Add a dark 'blueprint' effect

Inverts the image, applies false colour and a vingette.

* TTMapImage gains the ability to read colours from the filters in the defaults array.
* TTMapImage respects a boolean key `disableAffineClamp` in the filter dictionary. Vignette doesn't work with AffineClamp in place.

Preview:
![map-97065e939d5f97c95af4986b66c9f697](https://cloud.githubusercontent.com/assets/421031/5072945/2ad85262-6e76-11e4-9e9a-5ba15fbc6d71.png)

Ref tomtaylor/satellite-eyes#34