Deposit loading

[lvshaoping007]

1. change deposit loading to small loading to avoid UI not updating for a long time

[pro-wh]

thanks!

more detailed summary of changes from my reading of the code:

• approve + deposit takes a while, in part because it's multiple transactions
• this process was previously the same as any other transaction, which puts up a modal spinner
• this makes it not block out the UI anymore--actually I only understand this from the author's description, and I don't know about the implementation in the code
• in order to let users still keep track of ongoing allow+deposit, there's a new area in the extension state, called the "local cache" of approve and withdraw transaction hashes that we know we're watching out for. it's backed by localstorage
• there's new UI (in the paratimes tab?) that keeps an eye on these transactions in the local cache
• this cache stuff comes after the submitTx, so I think it shouldn't cause any trouble with overlapping transactions and nonce management
• maybe unrelated, there are some change to the API wrapper, doing something relative and absolute URLs. @lvshaoping007 can you explain that?

the management of this new "local cache" looks pretty reasonable. but additional thoughts:

• there's something in here about these +-separated strings in the local cache. what does this design get us, compared to having it be a 3-element array?