Solidity template with hardhat and dapptools

This is a solidity template with hardhat and dapptools.

• put the solidity contracts files under src/contracts
• put the dapptool related test files under src/test

for import modules errors, update file remappings, for example:

@openzeppelin=node_modules/@openzeppelin/
@chainlink=node_modules/@chainlink/

try run dapp update if there is no ds-test under lib folder