#15 latency interface for conductor

[Roger B. Dannenberg]

Need interface for tap latency: osc_tap, spacebar_tap, button_tap. Probably this should be a menu item to open a new window with sliders so you can adjust them while listening. Window should be closable and of course latency parameters go to preferences (for Conductor app).

[Shuqi Dai]

commitment [r525]
Title: Add latency adjustment interface for conductor
Description:
When click ‘Latency Adjustment’ button in conductor, open a new window for user to adjust three latencies including OSC Foot Tap Latency, Button Latency and Spacebar Latency.
Three sliders for adjusting each latency (range 0 - 100 ms)

1. Three 'Reset' buttons for setting each latency to its default value (store in latency class)
   Once close ‘Latency Adjustment' window, save the latency preferences automatically.
   Modification:
   Add Latency class in latency.srp to store all latency information
   Add Latency Handler class in interface.srp to handle latency adjustment

PS: the modification in player.srp is for the bug of stopping when paused, will be explained in later commitment in midi_player