Prevented duplicate binding of upload button on debug importer

Fixes #1899
Merge pull request #1900 from schneidmaster/fix-1899

Prevented duplicate binding of upload button on debug importer
Improve errors on image upload
No select or text cursor on rendered preview

fixes #1595

- prevents the backspace key from doing terrible things
Merge pull request #1904 from ErisDS/issue-1595

No select or text cursor on rendered preview
Ensure cookies are only ever set for admin

fixes #1901

- Adds a trailing slash to the cookie path
- Resolves random log-outs
- Adds a test which proves the case
Merge pull request #1910 from ErisDS/issue-1901

Ensure cookies are only ever set for admin