audit fixes

[Zartaj0]

This PR contains chages for the following issues:

1. Remove redundant boolean check
2. Removed unused variable
3. Fix redundant leaf creation
4. Remove unnecessary return keyword
5. Fix typo in comments
6. Added safeERC20 instead of IPUSH for transfers
7. Added an event for epoch initiation.
8. Fix natspec for release event.
9. Fix natspec for lock function.
10. Update readme with the latest changes
11. Validate the total amount off-chain and on-chain
12. Add permit functionality for locking

Remaining issues with no changes in this PR

1. L-06 - We have decided to keep it, as we are only putting the check on the recipient, allowing the smart accounts to lock their tokens but not allowing them to make a contract recipient.
2. L-07 - In discussion.
3. L-10 - This has no specific fix in the code. We will use pause/unpause effectively to avoid these scenarios.
4. L-12 - As stated earlier, there will be one Merkle root per epoch, which will only be calculated after pausing the locker and release contracts.
5. L-15 - Those scripts are not used anywhere important. They are just for debugging.