feat: Introduce Asset Scale for fractional asset support (#301)

* adds asset scale to the vault spec

* restores vault_info example

* changes AssetsMaximum internal type to Number

* improves  documentation

* adds destinationTag to VaultWithdraw

* specifies assetScale behaviour for different vault assets

* renames scaleFactor to scale to reuse existing field name

* fixes post merge issues

* addresses code review comments

* improves AssetScale description

* adds updated date

* cleans up formatting after merge conflict resolution

* address formatting issues

* improves MPT scale description

* Update README.md

Author: Tapanito