loam storage: smaller key names for optimizing storage

[BlaineHeffron]

Iterate over the names and use something like 0, 1, 2 etc to minimize storage cost of keys.

[BlaineHeffron]

The main issue is migration. If the keys are assigned based on some mapping they need to be the same if other storage keys are added to the contract and the contract is redeployed. This way existing storage would still be accessed properly.

[BlaineHeffron]

After discussion with Willem, the name shortening should be done via some sort of manual entry if the user wants it so that the user is responsible for making sure there are no name collisions.

The user can also opt out of the storage name being preprended to each key.