add auto-completion for narration

[dtrai2]

third time's the charm

I accidentally deleted my changes again and closed the pull request #1816, luckily we have something like git reflog with which I could reconstruct it.

Anyways this is still my attempt to add the auto-completion feature for the narration text field. It is still not perfect, but I didn't want to let the changes go to waste. Maybe it's good enough like this or someone might help out to finish it (see my last comment on #1816).

closes #1535, #1145

[yagebu]

This part is problematic. In my case, all these narrations would e.g. double the size of the balance sheet report. I think we should switch to lazily loading them only when the dialog is used.

[dtrai2]

okay yeah, I can understand the problem. Can you give me a hint for a possible implementation though? Or do you have something similar inside the repo where I could get some inspiration?

I just looked at it and with my current understanding I would have to remove the narrations from the get_ledger_data() method inside internal_api.py and instead create another endpoint in json_api.py which is then somehow called once the dialog is opened? Is this remotely a good way to solve this or is there maybe an easier way?