Silkscreen color not being parsed

```silkscreen``` is only set if the SparkFun or SparkX logo is seen.

The Panelizer isn't aware of the new SparkPNT logo - and so silkscreen is never set.

Two changes are needed:

- Set the ```solderMask``` and ```silkscreen``` if the SparkPNT logo is seen
- Set ```silkscreen``` correctly if silkscreen, Silkscreen or SILKSCREEN is found in the drawings