Use buttons instead of icon to start recording

[Sergey "Shnatsel" Davidoff]

Instead of using an icon on the top of the window, use "Record" and "Cancel" buttons on the bottom.
Rationale:
 - It's not obvious that an icon is clickable, and that it triggers an action. Use a button instead.
 - the user should start recording only after they set the proper settings. Since most people read from top to bottom, the button that starts recording should be on the bottom of the window.

"Cancel" button should be on the left and "Record" on the right, see http://elementaryos.org/docs/human-interface-guidelines/ui-toolkit-elements/windows/dialogs