Having the export button at the top was confusing people into thinking
the entire wallet was exported.
This commit moves the export button to the address book, receiving
addresses and transaction tabs separately.
- adds 6 methods in BitcoinGUI to access some actions needed by the new
WalletView class
- updates WalletView class to use these instead of trying to duplicate
these
- cleanup walletview.{cpp/h} and remove all unneeded stuff
- this fixes problems with tabs toolbar (#2451) and export broken (#2436)
- more details in #2447
- the send coins context menu entry was not working anymore, because
a non current version of #2220 was merged onto current master
- also removes some unneeded spaces and adds a comment to
WalletModel::getNumTransactions()
