Synchronizing Status and Refresh action

[chikeichan]

Currently, sync/unsync is already integrated. However, when the extension is first created, we need a third state -> synchronizing

DoD:

• Ask for design, but we can move ahead with a [spin] Synchronizing.. yellow text
• the SPV node only give us sync/unsync state. Synchronizing = Node is out of sync, but is receiving blocks. Unsynchronized = Node is out of sync and is not receiving blocks.
• If a node is truly Unsynchronized, there is a refresh button that currently has no action. We should refresh the background.html page when user click refresh. Note that this is a naive approach. If a node is not syncing, most likely there are other things we must do to fix the node (for example, clearing indexDB and starting over)