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.
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
Merge branch 'master' of github.com:spesmilo/electrum into clean