Material UI: upgrade modals

Also clean up the Create Torrent page, delete some redundant CSS, prevent click-and-drag inside a TextField from moving the whole window, and make all label and input fonts  a consistent 14px size.

src/renderer/components/modal-ok-cancel.js

@@ -0,0 +1,24 @@
+const React = require('react')
+const FlatButton = require('material-ui/FlatButton').default
+const RaisedButton = require('material-ui/RaisedButton').default
+
+module.exports = class ModalOKCancel extends React.Component {
+  render () {
+    const cancelStyle = { marginRight: 10, color: 'black' }
+    const {cancelText, onCancel, okText, onOK} = this.props
+    return (
+      <div className='float-right'>
+        <FlatButton
+          className='control'
+          style={cancelStyle}
+          label={cancelText}
+          onClick={onCancel} />
+        <RaisedButton
+          className='control'
+          primary
+          label={okText}
+          onClick={onOK} />
+      </div>
+    )
+  }
+}