fix some cosmetic glitches in the codebase

- rename URL into URI in paymentserver where correct
- add some missing Qt-coding-stuff in paymentserver
- change QSpinBox to QLineEdit as base for BitcoinAmountField in .ui files
  (as this is the result when converting the BAF back into base)
- remove some c_str() and replace with QString::fromStdString()
- remove several new-lines
- remove unneeded spaces
- indentation fixes

src/qt/askpassphrasedialog.cpp

@@ -16,6 +16,7 @@ AskPassphraseDialog::AskPassphraseDialog(Mode mode, QWidget *parent) :
     fCapsLock(false)
 {
     ui->setupUi(this);
+
     ui->passEdit1->setMaxLength(MAX_PASSPHRASE_SIZE);
     ui->passEdit2->setMaxLength(MAX_PASSPHRASE_SIZE);
     ui->passEdit3->setMaxLength(MAX_PASSPHRASE_SIZE);