Update crowdsales.md (#1822)
Update crowdsales.md (#1822)

Change reference to Tokens documentation
Fix typo `CROWDALE_ADDRESS` to `CROWDSALE_ADDRESS`

Resolve compilation errors in sample contracts:
* Change `address wallet` to `address payable wallet` in multiple sample contracts
* Change `ERC20 token` to `IERC20 token` in multiple sample contracts
* Reorder inheritance of crowdsales to prevent error: "Linearization of inheritance graph impossible" in multiple sample contracts
* Change `startTime` to constructor parameter `openingTime`
OpenZeppelin/openzeppelin-contracts,OpenZeppelin/zeppelin-solidity,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/zep-solidity,OpenZeppelin/zep-solidity,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/zeppelin-solidity