Optimize gas costs when handling liquidity start and end times
When the `LiquidityMining` contract is deployed, `startLiquidityMiningTime` saves the current block timestamp.\\n```\\nstartLiquidityMiningTime = block.timestamp;       \\n```\\n\\nThis value is never changed.\\nThere also exists an end limit calculated by `getEndLMTime`.\\n```\\nfunction getEndLMTime() public view override returns (uint256) {\\n    return startLiquidityMiningTime.add(2 weeks);\\n}\\n```\\n\\nThis value is also fixed, once the start was defined.\\nNone of the values change after the contract was deployed. This is why you can use the immutable feature provided by Solidity.\\nIt will reduce costs significantly.\\n```\\ncontract A {\\n    uint public immutable start;\\n    uint public immutable end;\\n   \\n    constructor() {\\n        start = block.timestamp;\\n        end = block.timestamp + 2 weeks;\\n    }\\n}\\n```\\n\\nThis contract defines 2 variables: `start` and `end` and their value is fixed on deploy and cannot be changed.\\nIt does not need to use `SafeMath` because there's no risk of overflowing.\\nSetting `public` on both variables creates getters, and calling `A.start()` and `A.end()` returns the respective values.\\nHaving set as immutable does not request EVM storage and makes them very cheap to access.
Use Solidity's immutable feature to reduce gas costs and rename variables for consistency.\\nUse the example for inspiration.
```\\nstartLiquidityMiningTime = block.timestamp;       \\n```\\n