Filtering expenses list by category

Signed-off-by: pianomister <stegiemail-github@yahoo.de>
Cleanup

Signed-off-by: pianomister <stegiemail-github@yahoo.de>
Expense lists are updated after changes are made to containing items

Signed-off-by: pianomister <stegiemail-github@yahoo.de>
Introducing synchronization of categories and accounts

Signed-off-by: pianomister <stegiemail-github@yahoo.de>
Merge pull request #5 from pianomister/master

Full synchronization and list features