PostGIS wktraster Integration Part 1: Documentation

[robe]

This is related to #337, but since I'm going to be stuffing this in the PostGIS code base, figure I better put it here as well and maybe merge the two tickets later.

Since we have all the plumbing already built in PostGIS codebase to build PDF documentation and hmm we plan to eventually merge the two projects, it seems to me we should start now and start at the easiest part (at least for me), start building the documentation in the same style as PostGIS documentation.

I'm going to have separate xml files for the wktraster, first by starting with function reference since I'm finding it hard to figure out how to use the functions simply by the wiki help and also figuring out which functions are even done without constantly referring to the code and tickets.

The wktraster_reference.xml will just have reference to the functions that are present in the code base with link back to wiki for more info. Similarly will have an xsl to build the raster postgresql comments and test harness for it.

By keeping the xml files separate, it will be easy to pull them out as separate documentation or integrate them in more into the core documentation.

The documentation will be built as a single pdf. With WKT raster sections following the PostGIS reference sections for now.

If any one has issues with this, speak now. I will assume silence as a vote to proceed.