[GRASS5] gis.m: Loads as a package

[Cedric Shock]

Hi,

I made a package index for most of the files in gis.m. I swapped out most of 
the "source"s in gm.tcl for lazy loading in the package. This makes the layer 
types, for example, not be loaded until someone actually uses them. On my 
reasonably slow and reasonably old computer gis.m now loads in just over 2 
seconds if wish has been recently run (and thus its files are in memory 
cache) or if it's currently running (no loading ".so"s).

--Cedric