[pdal] initialize() and its after effects

[Howard Butler]

Michael,

Consider the following:

Writer->Scaling->Reproj->Descaling->Reader

I don't want to specify the input SRS for Reproj, because it is already available from the Reader.  Well, kind of.  It's available to the reader at initialize() time, because I am going to override whatever the reader actually has at runtime (in many cases, this is None).  Our current behavior has the Reproj filter being initialized() before the Reader, however, so we'll end up forwarding an empty SRS.

I think what I should do in this scenario is delay Reproj filter's OSR initialization until after the pipeline is initialized (readBegin()).  Agree?

There are a number of other gotchas that seem to be cropping up now that we've moved to the initialize() model (which I like).  Things like LASWriter::setPointFormat(), etc needing to happen before initialize().  We need to audit a bit and see which things that were dumped in initialize really should belong in readBegin/writeBegin, and which really belong in initialize.  

Howard