feature: type/store.js leveldb integration

[victorwu]

#Summary

This feature integrates leveldb database storage functions into types/store. This would enable further account and identity storage, allowing users to have better profile management when accessing various fabric applications. Functions in fabric-browser-extension have also been migrated to use types/store in @fabric/core.

• updated level to latest version, including updating code syntax
• added leveldb functions
  • createDB, initDB, clearDatabase,
• added account functions
  • setSeedPhrase, insertAccount, insertIdentity, getAccountValid, retrievePrivateKey, getIdentityCount
• added settings config functions
  • setDBIdentityCheckState, getGlobalChainState, getAccount, checkPassword, changePassword