Using macro to define Poly-line structuring elements

Change-Id: I2dbfcf4794d93059edf0ca1bc8702f3b7c71b6a9
Re-factored common base methods to ProcessObject base

Created new base class for ImageFilters to contain common methods such
as setting the number of threads, debugging, and call-backs/commands.

Change-Id: I2902c55a03d6ad73f3fb08b491637b454f1aa504
Add ProcessObject number of threads parameter

Change-Id: I061c07345e05923e29273a1ff4242818e8dfdcfd
Merge topic 'SIMPLEITK-447_AddProcessObjectBase' into next

2e187c1 Add ProcessObject number of threads parameter
de8ddd6 Re-factored common base methods to ProcessObject base
Merge topic 'SIMPLEITK-431_AddMorphologyKernelEnum' into next

ee4cf9d Using macro to define Poly-line structuring elements