Optimized current featurres and added new account transfer featurs.

Current Features Enhancements: 
- savings_account to savingsAccount
- maxi_savings_account to maxiSavingsAccount
- removed dead code  
- removed unused imports
- added method getAccountType
- ensured all instance variable are private with appropriate getter methods

New Features Enhancements
- A customer has ability to transfer between their accounts
- Added a method, isWithdrawnRecently(int dayLimit) for maxi-Savings account interest calculation check

To Do
- Change Maxi-Savings accounts to have an interest rate of 5% assuming no withdrawals in the past 10 days otherwise 0.1%
- Interest rates should accrue daily (incl. weekends), rates above are per-annum