started mixer activity and added functions
small edit
Add new sounds and fix lfour.wav

lfour was saved at 48khz to demo the resampling, but the resampling does
not work well enough to demo.
edited mixer and mix
Merge branch 'master' of https://github.com/Ilikecattle/EECE381Module2
<Android & DE2> Updates: See Below
-SkipNext and SkipPrev now function as expected
-Pause now stores position of the song for resume
-SeekBar now stop and replay the music at the assign position
-Sync curr_song_id
-Playlists on Android works properly now
-Multiply songs are able to added to playlists and played with SkipNext and SkipPrev through the songs in the list
-ActionBar for going to different Activity now function as expected; ActionBar added in SongActivity
-Playlists information with Songs in the lists are now update with SD card once quitting the application
<Very Important> Incorrect text files can cause the system crashing, make sure the application is always properly close
If the application is crashed, please deleted LISTS.TXT, LSONG.TXT, and LORDER.TXT and recompile DE2 before starting the application again.
<SDFiles>LISTS.TXT, LSONG.TXT, LORDER.TXT