Update GAPIL readme to describe maps.
Update GAPIL readme to describe maps.

pmuetschard/gapid,google/gapid,google/gapid,pmuetschard/gapid,google/gapid,pmuetschard/gapid,google/gapid,google/agi,google/gapid,google/agi,google/agi,google/agi,google/agi,pmuetschard/gapid,pmuetschard/gapid,google/agi,pmuetschard/gapid,google/agi,google/gapid,google/gapid,pmuetschard/gapid,google/agi,google/gapid,pmuetschard/gapid