Follow up tasks

[epogrebnyak]

• Separate income statement from close()
• allow Chart to include FastChart and names
• deduplicate add account methods
• generate Excel file
• opening entry
• printing to console (viewers)
• account naming as asset:cash
• fix file names and allow setting a directory

[epogrebnyak]

Flat entry store

[epogrebnyak]

Setter can be defined better (in core.py)