Add ptree nodes for all selected points.
Set scale to .01 for las writer.
Merge pull request #443 from PDAL/issues/307-badinfo

Add ptree nodes for all selected points.
Merge pull request #444 from PDAL/issues/442-las-scaling

Set scale to .01 for las writer.
Don't set default values for scale/offset - already set in xform object
ctor.
Merge pull request #446 from PDAL/scaleinit

Don't set default values for scale/offset - already set in xform object
Programmable filter can add dimensions to context

Using one or more `add_dimension` options on a programmable filter will
instruct the filter to add those dimensions to the primary
PointContext. This way, the programmable filter can set dimensions that
might be present on the PointContext.