print error message on unhandled rejection for non-chrome

fixes #570
if notebook load fails somewhere after the gist part, don't keep trying

we were going into a death loop on safari because of some random other
incompatibility in our code

for #809
remove obsolete performance log

it was bombing on safari
fixes #809
Merge branch 'hotfix/1.1.2' into develop

Conflicts:
	htdocs/editor_tab.js
	htdocs/js/rcloud_bundle.min.js
autoremove progress bar

fixes #592 (again)
set CRAN mirror option in repos if not already set
update NEWS
port a6e30b0,16cb0ce from develop
bump VERSION
remove defunct log for @sujitbehera27

(don't worry we all leave debugger statements and console logs in our
code... we all get called out for it too ;-)
promisify file upload and separate UI from guts

i think this helps with multiple file upload too
repair error handling for asset upload
multiple file upload, allow replacing upload ocaps

fixes #649 multiple file upload (actually probably with the UI split earlier)
closes #768 allow specifying file upload path
update NEWS
Merge branch 'feature/upload-many-files' into develop
Merge branch 'develop' of https://github.com/att/rcloud into develop

Conflicts:
	NEWS.md
Merge branch 'hotfix/1.1.2' into develop

Conflicts:
	NEWS.md
	VERSION