Issue #121: Move AssetDefinition and AssetDefinitionManager out of Wallet Model

* refactored AssetDefinition and AssetDefinitionManager to use colormap instead of model
* moved make_operational_tx_spec from AssetDefinition to BasicTxSpec
* moved AssetDefinition and AssetDefinitionManager into ngcccbase/asset.py
* added unit tests for asset.py in tests/test_asset.py
Issue #121: Move Address-related stuff out of wallet_model

* Moved AddressRecord and LooseAddressRecord into address.py
* Moved DeterministicAddressRecord and DWalletAddressManager into deterministic.py
* Moved BIP0032AddressRecord and HDWalletAddressManager into bip0032.py
* Added unit tests for all 3
* Fixed a couple bugs related to importing loose addresses
Merge pull request #124 from jimmysong/121c

Move more stuff out of wallet_model