* arts-2-1-705

	* doc/uguide/absorption.tex: Added sections on
	propmat_clearskyAddFaraday and propmat_clearskyAddParticles. Added info
	on setting isotopologue_ratios. Moved input-to-LbL paragraphs into their
	own subsection (it's not only for LbL. and that way we have a proper
	place to document how to set iso ratios). Minor updates (it's propmat
	now!), rewording, re-layouting, spellfixes...

	* doc/uguide/references.bib: Zeeman paper added.

	* doc/uguide/absorption_theory.tex: Updated info on isotopologue ratios
	(not hard-coded anymore!)

	* doc/uguide/clouds.tex: Section label added.

	* doc/uguide/symbol_defs.tex: \chem makro added.

	* src/workspace.cc, methods.cc: Sorted some stuff in its
	(alphabetically) right place (particularly propmat*). In abs_speciesSet
	added clear note that order of tag groups matters.

	* src/gas_abs_lookup.cc (Adapt): Error message improved(?).



git-svn-id: https://www.sat.ltu.se/svn/rt/arts/trunk@8550 aaf1aab0-4228-0410-ad68-8dceda47f409