fixed a small typo

changed databse to database
allow gridfs objects to use non ObjectID ids
mapReduce; auto-convert scope functions to Code
white space
Merge pull request #822 from bodokaiser/patch-1

small typo in collection doc
Merge remote-tracking branch 'aheckmann/mapReduceScope'
Merge remote-tracking branch 'nailgun/fix_gridfs_objectid2'