Fix bug. Output the feature value not the pot id.

* timestream/manipulate/pipecomponents.py: We get the feature values
from pot.getCalcedFeatures()[fName]
Add perimeter calculations.

* timestream/manipulate/plantSegmenter.py: Add perimeter calculations.
We also removed the label calculation from area.
Add roundness to the feature calculation.

* timestream/manipulate/plantSegmenter.py: Add new roundness method.
Add the csv files to a directory under outputroot.

* timestream/manipulate/pipecomponents.py (__init__): We default to
os.path.join(context["outputroot"]), "csv")
Add compactness to the feature calculations.

Its commented out for now pending solution to
 https://github.com/scikit-image/scikit-image/issues/1075
* timestream/manipulate/plantSegmenter.py: Use skimage's "Solidity" to
calculate compactness.
Add eccentricity to the feature calculation.

The code is commented out for now as there is a bug with skimage:
https://github.com/scikit-image/scikit-image/issues/1075
* timestream/manipulate/plantSegmenter.py: We use skimage's eccentricity
option.