add some convenient methods for BinData and UUID

MongoDB shell version: 1.9.1-pre-
> help misc
b = new BinData(subtype,base64str) create a BSON BinData value
b.subtype() the BinData subtype (0..255)
b.length() length of the BinData data in bytes
b.hex() the data as a hex encoded string
b.base64() the data as a base 64 encoded string
b.toString()

b = HexData(subtype,hexstr) create a BSON BinData value from a hex string
b = UUID(hexstr) create a BSON BinData value of UUID subtype
b = MD5(hexstr) create a BSON BinData value of MD5 subtype

o = new ObjectId() create a new ObjectId
o.getTimestamp() return timestamp derived from first 32 bits of the OID
o.isObjectId()
o.toString()
o.equals(otherid)