North Saami adposition lexicon

First come the 3 continuation lexica, the division is based on Nickel
and should probably be revised. Then comes the adpositions themselves.
The uninflecting ones are pointed to the 3 tag lexica, the Px ones to the
Px lexica in sme-lex.txt and closed-sme-lex.txt.


 * __LEXICON Pp   __ gives both +Po and +Pr

 * __LEXICON Postp   __ gives +Po

 * __LEXICON Prep   __ gives +Pr


 * __LEXICON Adposition   __ is the lexicon with the adpositions