s/cogent.util.misc.app_path/bipy.app.util.which/g

Replace usage of ```cogent.util.misc.app_path``` with ```bipy.app.util.which```. Remove ```qiime.util.which```.

Related to #1369.
fix import spacing
Merge pull request #1379 from jrrideout/issue-1369-which

s/cogent.util.misc.app_path/bipy.app.util.which/g