Asset: move depreciation to one or more separate tab/s, per Finance Book

[bosue]

Currently, an Asset’s depreciation with all its complexities is shown on the main and single tab.

If more than one Finance Book is being set up for depreciation, we‘re currently skipping the schedule and its graph, as there would have to be more than one.

Instead I‘d propose the following:

• Keep the “Calculate Depreciation” checkbox and a simple Finance Book selector on the main tab.
• Implement a combined graph showing all Depreciation Schedules on top of the main tab.
• Move everything else, including all the depreciation settings and schedules to their own tab per Finance Book.
• As soon as Finance Books are fully fleshed out, do the same for Accounts.

[anandbaburajan]

@bosue sure, you can take it up 😄. I'm the primary maintainer of the assets module, so assigned it to me.