Enable run tortuosity button only when a valid node is present
Enable deletion of spatial object nodes
Add option to save the tortuosity arrays as an CSV file

This implies a little bit of refactoring/enhancing:
 - Add All flag (0xFF) so we can run all the metrics
 - Refactor the GetArray(s) methods to clarify when the array is created
or not. To this end, a GetOrCreateArray method was added. Internaly, we
use templated method so we can any type of array.
  - Automatically add the NumberOfPoints integer array on each computation
of tortuosity. For each vessels, this array values tells the user how many
point this vessel has. It can be used (like in SaveAsCSV) to only get one
measure value per vessel instead of on measure value of each point of the
vessel.

By default, the csv does not list the InflectionPoints array since it only
makes sense to look at it when we look at all the points of the vessels.
Move logic's tortuosity computation to a TubeTK filter - 1/2

Create a filter in TubeTK that does exactly what is done in the Tortuosity
module logic for a given single vessel. This will allow the tortuosity
measure to be more easily used by people.
Move logic's tortuosity computation to a TubeTK filter - 2/2

Use the new filter in the logic.
Fix Tortuosity module compilation

Include filtering directories. No need to link against any library since
the filter used is templated.

Change-Id: Ie8b98ef7802a5e017aec4d58abb0b5a2ebc34f01
Fix Tortuosity filter and make sure it passes the test

A few things here:
 - Fix test comparison value
 - Fix normalizations to make sure we don't divide by 0 and get NaNs
 - Remove completly useless dynamic_cast
 - Misc fixes of codes badly rewritten when switching from the logic to
a filter
 - Add epsilon parameter for future testing of the filter.

Change-Id: I0af3c60c7ccb4f00601a3da82bd7b6cb9ff93945
Merge pull request #355 from vovythevov/TortuosityModule

Tortuosity module