fill out basic docs for the core functions
fill out basic docs for the core functions

HeliumProject/mongo-c,Elastica/mongo-c-driver-legacy,mongodb/mongo-c-driver-legacy,HeliumProject/mongo-c,Elastica/mongo-c-driver-legacy,mongodb/mongo-c-driver-legacy,HeliumProject/mongo-c,mongodb/mongo-c-driver-legacy,HeliumProject/mongo-c,Elastica/mongo-c-driver-legacy,Elastica/mongo-c-driver-legacy,mongodb/mongo-c-driver-legacy