Fix typos, add safety check on share

Previously, inserting rows could fail and cause a database error; now,
existence of the row is checked before attempting insert
Add un/share functions to Study

And tests
Merge branch 'master' of https://github.com/biocore/qiita into share_and_public_buttons-issue-476
Change order of columns in private studies

Lumps PI and Shared together, since they are more closely related
Add owner property to Study

And test
Add owner column to shared, public study display
Add chosen to sitebase
Add function go iter over all users
Add sharing for studies
Fix typo, waiting_approval -> awaiting_approval
Do not allow sharing with self
Add test for share w/ self; follow id convention

thanks @squirrelo!
Merge pull request #546 from adamrp/share_studies-issue-476

Share studies issue 476