Remove Grease as dependency?

[tinchodias]

The BaselineOfMongoTalk loads Grease as a requirement for Mongo-Squeak. The dependency checker shows that effectively that's the only package that references Grease, more exactly the GRCodec class (with GRCodec forEncoding: 'utf8').
Probably there is some alternative to avoid depending on Grease.

[tinchodias]

This is how the codec is used from LittleEndianStream class (Mongo-BSON package):

^ GratuitousIncompatibilities utf8Codec decode: string.

Probably it can be rewritten with ByteArray>>utf8Decoded.

[tinchodias]

Very close to #72.