Remove trailing spaces in SAC model parallel line
Split line and parallel line models into separate 'cpp' files
Fix documentation for SAC model parallel line
Add const qualifiers in SAC model parallel plane
Fix angular distance condition in SAC model parallel line

The old condition checked if the line model is perpendicular to the axis
provided by user, while according to the name of the class and
documentation it should rather check if the line model is parallel to
the axis.
Add a test for SAC model parallel line

Additionaly rename test_sample_consensus_line_model to reflect the fact
that now it tests multiple line models.
Merge pull request #969 from taketwo/fix-parallel-line

Fix behavior of SACMODEL_PARALLEL_LINE