Reduce computation time for bilateral upsampling.

Compute the distance values (exponential functions) in advance to reduce computation time.
Add: approximate version of the progressive morphological filter

This version is closer to the original paper and significantly faster,
computing the morphological operations on a 2D grid.
Merge pull request #665 from chambbj/approx-pmf

Add: approximate version of the progressive morphological filter
Merge pull request #689 from aikkala/bilateral_upsampling_fast

Reduce the computation time needed for bilateral upsampling
reset camera by default in pcd_viewer
Merge pull request #693 from xiangxw/pcd_viewer_reset_camera

reset camera by default in pcd_viewer
Merge branch 'master' of https://github.com/PointCloudLibrary/pcl into sandbox