Add spinner for fetching transactions

[osdnk]

Motivation

There're a lot of things happened before making list of transactions visible and especially when there's a lot a them it's reasonable to display a feedback indicating that user is supposed to wait for a while.

Changes

Some conditions has to be filled in situation when spinner has be to be displayed. Transactions have not to be fetched for the first time, there have to be not loaded from storage (array of them has to be empty) and AddFundsInterstitial shouldn't be visible.

I achieved it by hooking into fetching process and tracking state of fetching in store by special hoc.