add sphinx/doc_readme.txt

This file explains how to generate the manual.pdf
copy pdf into main folder after compiling

the default location _build/latex/ is inconvenient...
fix package/module python weirdness

We no longer import constants in __init__ so that it works without
installing.
extract debye test, cleanup
remove unused code from seismic
Merge pull request #51 from tjhei/crazy_init_fixes

Crazy init fixes
Merge pull request #45 from tjhei/add_pdf_readme

Add pdf readme
Various fixes to manual text.

Cleaned up some references, grammar, etc.
More minor changes

Fixes in manual
More changes

Various and sundry
Merge branch 'Cay_man' of https://github.com/lordkman/burnman into Cay_man