Improve the logic of the complex balance

[ihoroleksiienko]

Main changes

1. The possibility to transfer frozen balance even if the related tokens are restricted has been added. E.g.:
   • The X account has 100 tokens in total.
   • 100 tokens are restricted to transfer only to account A.
   • 10 tokens are frozen and expected to be transferred to account B.
   • Despite of the restricted balance, the transferFrozen() function can transfer all 10 frozen tokens from X to B. Previously it did not work. The transferFrozen() function could only transfer tokens from X to the purposed account A.
2. All error checks related to complex balances have been moved from the internal _afterTokenTransfer() function of specific base contracts to the same-name internal function of the CWToken base contract. It allows to concentrate the check logic of the complex balance in a single place instead of spreading it among multiple functions.
3. Redundant internal functions have been removed.
4. The tests have been updated to properly cover the updated logic.
5. The new complex tests have been added to check the transferFrozen() function when other limitations exist.

Test coverage

New functionality was fully covered with tests.