Uncouple filesystem between qiita main and plugins

[sjanssen2]

plugin	plugin changes	status	use testing code	clean post-test-dirs
qp-deblur	jlab/qp-deblur#2		yes	---
qtp-biom	jlab/qtp-biom#2		yes	---
qp-target-gene	jlab/qp-target-gene#3	(update client first)	yes	---
qtp-sequencing	jlab/qtp-sequencing#4	(investigate!!)	yes	---
qtp-visualization	jlab/qtp-visualization#2		yes	---
qtp-diversity	jlab/qtp-diversity#2	(update client first)	yes	---
qtp-job-output-folder	jlab/qtp-job-output-folder#2	(update client first)	yes	---
qp-qiime2	jlab/qp-qiime2#2		yes	---

qiita: qiita-spots/qiita#3483
qiita_client: qiita-spots/qiita_client#59
tinqiita: #55