Round up tx fees for better UX

[olanod]

Balances like 0.999999912345 are quite ugly and after certain number of decimals users don't usually care if the fee is 0.000001 or 0.00001 more expensive. We should have a minimum fee that is quite cheap and also used for rounding things up.

This rounding can be based on the existential deposit(e.g. ED/10) but first I would suggest to also adjust the ED to something rounder. It's currently configured to be 1/10th the ED of Kusama which is based on the const QUID: Balance = UNITS / 30. I propose our new ED to go form 0.000033333333 to 0.000100000000(even higher?) and the rounding factor/minimum fee to be 1/10th of that(0.000010000000). For other assets we can follow a similar strategy based on their minimum balance.