Update Utmost contract to UtBase

[deepesh-kn]

Update Utmost->UtBase implementation (3)
- Rename Utmost to UtBase
- Remove UtilityToken dependencies from UtBase
- The mint function of UtBase needs to perform 2 operations
- Call internal _mint function of ERC20 token.
- Unwrap the token to get the base token.
- In the current implementation, the mint external function is defined in the UtilityToken.
- In order to unwrap the token, the mint function needs to be overridden, resulting in to bypass the calls to Utility token.
- ERC20Token already has _mint, _burn and _burnFrom internal functions. Currently the UtBase is UtilityToken, remove the dependencies of UtilityToken and directly use the functions from ERC20 token.
- The mint function in the UtBase can only be called by ConsensusCogateway address.
- The mint external function should not emit Transfer event as its already handled in the _mint internal function of ERC20Token..
- The mint, burn and burnFrom functions must not return boolean value.