Add the Logger class.

- Add LOG_DEBUG and LOG_ERROR macros.
- Initialize the logger in the main() function.
Add the first database migration.

- Add the database migration resource file.
Add the Database class.

- Initialize Database in the main() function.
Add 'type' property to Account.
Add AccountModel class.
Update the Logger class.

- Changed comment style.
- Changed getInstance to instance.
- Add global.h.
- Add NO_COPY_AND_ASSIGN macro.
Style update.
Style and documentation changes.
Rename getInstance to instance.
Add roleNames method to AccountModel.
Replace accounts property with AccountModel.
Load the account model on application startup.
Add account type based getter functions.

- add AccountModel::assetAccounts()
- add AccountModel::expenseAccounts()
- add AccountModel::incomeAccounts()
- add AccountModel::liabilityAccounts()
Replace log macros with with QT message calls.

- Removed LOG_DEBUG and LOG_ERROR macros.
- Removed LogLevel::ERROR.
- Add LogLevel::{WARNING, CRITICAL, FATAL}.
- Add Logger::messageHandler.
Add RootMenu.qml