Consolidate jQueryUI buttons into _buttons.scss

Fixes: CNVS-16353

- Moved jQueryUI button classes into main button
  components stylesheet, so we now have all button-related
  styles in a single place.
- Kept jQueryUI button set styles in their own
  stylesheet.
- Moved .Button disabled styles out of the canvas-button
  mixin because there was no longer any reason to make
  them part of the mixin.

Change-Id: I96d68efbb1fafc09e0d0d62c02eb886055da6434
Reviewed-on: https://gerrit.instructure.com/45354
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Colleen Palmer <colleen@instructure.com>
Product-Review: Colleen Palmer <colleen@instructure.com>
QA-Review: Anna Koalenz <akoalenz@instructure.com>
upgrade uploadify to 3.2.1

test plan:
 1. ensure you cannot inject HTML to uploadify.swf via the
    buttonText query parameter (see the example in Step 3
    of CNVVS-16665)
 2. regression test uploading files from old files page
    ("better file browsing" turned off)

fixes CNVS-16665

Change-Id: I9be3e20e4fb52649809ed5c9ed9824482575e209
Reviewed-on: https://gerrit.instructure.com/45572
Reviewed-by: Dan Minkevitch <dan@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>
admin roster users link to group's parent context

fixes CNVS-9828

test plan
- in a course with a TA and a teacher, create a group
- view the group's users page
- ensure that the teacher and TA are shown on the "Teachers & TAs"
 list
- ensure that the user name and avatars link to the course user
 page (/courses/:id/users/:id) rather than the group user page
 (/groups/:id/users/:id)

Change-Id: I9104322241b77a2904defc17f0d30a1f789a8532
Reviewed-on: https://gerrit.instructure.com/45575
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Andrew Butterfield <abutterfield@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>
Product-Review: Joel Hough <joel@instructure.com>