Added wicket-bootstrap dependency
Added Bootstrap CSS.
Added bootstrap hook up to application
Added bootstrap navbar to base page and included bootstrap css files.
Remove explicit CSS includes of bootstrap files since wicket-bootstrap injects its own.
Added relation between expense and category.
Fixed test class name
setCategory in expense service
addExpense renamed to create and returns the newly created expense
Added findAll method to category service
Added ability to create an entity model without a backing entity
Can now specify category when adding new expenses
Will now only load entity once if its backing a null entity.
Will only attempt to load if there is an identifier.
Added missing transactional annotation to set category
Verify date is not null when creating expenses
Verify description is not null when creating expenses
Verify description is not empty when creating expenses
Verify cost is > 0 when creating expenses
Added missing spring bean in test
Added missing bootstrap.js