No longer require restart for toggle exchange rate

Fixes issue #643 and allows fiat button to work without restart

No logic is required because Send tab gets removed and added for every
toggle.
Exchange rate update

use exchange rate value instead of string to calculate balance
Merge pull request #665 from wozz/exchange-value

Exchange rate update
installwizard: multisig wallets
fix #655
Merge remote-tracking branch 'upstream/master'
abstract and improve seed and key methods
more robust get_seed_text
fix: do not lower xpub
Merge pull request #662 from wozz/issue-643

No longer require restart for toggle exchange rate
lower default fee. fixes #403
simplify getseed: do not return hex
switch default display to mBTC
no accounts in multisig wallets
Add block explorer setting for "view online"
Litecoin: update default servers list
Merge remote-tracking branch 'upstream/master'

Conflicts:
	lib/wallet.py
Litecoin: update more labels and URLs
Merge pull request #667 from wozz/blockexplor

Add block explorer setting for "view online"
get_master_public_keys