Updated xrandr -q parsing to work with new output format.

The output format of xrandr -q changed slightly in recent versions (notice the 'primary' after 'connected' in DVI-0):

    Screen 0: minimum 320 x 200, current 2560 x 1024, maximum 8192 x 8192
    DisplayPort-0 disconnected (normal left inverted right x axis y axis)
    HDMI-0 disconnected (normal left inverted right x axis y axis)
    DVI-0 connected primary 1280x1024+0+0 (normal left inverted right x axis y axis) 359mm x 287mm
       1280x1024      60.0*+
       1152x864       75.0  
       1024x768       75.1     75.0     60.0  
       832x624        74.6  
       800x600        75.0     60.3  
       640x480        75.0     60.0  
       720x400        70.1  
    DVI-1 connected 1280x1024+1280+0 (normal left inverted right x axis y axis) 338mm x 270mm
       1280x1024      60.0*+
       1152x864       75.0  
       1024x768       75.1     75.0     60.0  
       832x624        74.6  
       800x600        75.0     60.3  
       640x480        75.0     60.0  
       720x400        70.1  


This patch updates monitor_switch.sh so that it works with the new format (and should still work with the old one). The new format is used in (at least) Mint 16 and above, and probably other distros too.