Remove several more obsolete KPP commands

[yantosca]

This PR removes several more obsolete KPP commands/keywords as described in #43.

docs/source/using_kpp/04_input_for_kpp.rst

• Add #AUTOREDUCE to the table of KPP commands
• Add a section for #AUTOREDUCE, linking to the detailed description in the Numerical Methods chapter.

site-lisp/kpp.el site-lisp/kpp_mecca.el

• Removed obsolete commands from font-lock-mode
• Reorganized list alphabetically

src/debug.c

• Removed RAD_SPC from function WriteSpecies
• Removed function WriteOptions (this is now redundant)

src/scan.h

• Removed RAD_SPC from the sptypes enum variable
• Removed function prototypes for DefineInitializeNbr, DefineXGrid, DefineYGrid, DefineZGrid

src/scan.l

• Removed obsolete keywords: DEFRAD, SETRAD, INITIALIZE, XGRID, YGRID, ZGRID, WRITE_OPT, USE, RUN, USES, SPARSEDATA

src/scan.y

• Removed obsolete tokens: DEFRAD, SETRAD, USES, SPARESEDATA, WRITE_OPT, USE, RUN
• Removed corresponlding entries from the "section" list
• Removed uselist and usefile entries
• Removed "case SETRAD" from setspcspc

src/scanner.c

• Removed xNr, yNr, zNr variables
• Removed obsolete functions DefienInitializeNbr, DefineXGrid, DefineYGrid, DefineZGrid, CmdSparseData, CmdUse, CmdRun,

CHANGELOG.md

• Updated accordingly

[yantosca]

Thanks @RolfSander. I'll merge it now.