Fix up GUI interactions with animation start/stop

[brucecrevensten]

• Clicking Pause button when in MapMode (not AnimationMode) no longer removes the visible overlay
• Play / Pause Buttons are enabled/disabled to prevent user from starting two overlapping animation sequences
• Colored the buttons, used standard Bootstrap classes: btn-success and btn-warning for playing/pause, respectively. Imperfect but OK I think.
• Pulls the map legend inside the Map when browser width is reduced (it was standing-off-from-left, which made it stick out in some cases).