Added note about pages being publicly viewable

STUD-1488
Upgrade JSdraw input.
moved Studio public Pages warning to a more prominent location
Added comment to getUserMedia call in photocapture.js
Translation fix in studio: For better translation

As the sentence in unit.html is splitted into three parts due to the varible release_date may be None, it breaks the integrity of a sentence.
Different language may have different word or event grammer order, so if a sentence is breaked into three parts, translators cannot adjust the word orders to create a good translation.
So this fix tries to combine the sentence together.
Make paver respect NO_PREREQ_INSTALL
Doc: update xblock publish() function signature
Merge pull request #3140 from edx/db/paver-respect-no-prereq-install

Make paver respect NO_PREREQ_INSTALL
Watch for asset changes.
Merge pull request #3121 from louyihua/translation-fix-cms

Translation fix in studio: For better translation in unit.html
Merge pull request #3135 from edx/hotfix/fix-jsdraw-input-2

Upgrade JSdraw input.
Merge remote-tracking branch 'origin/release'

Conflicts:
	requirements/edx/edx-private.txt
Merge pull request #3132 from edx/markhoeber/documentation/stud-1488

Added note about pages being publicly viewable
Merge pull request #3143 from edx/adam/merge-release-to-master

Adam/merge release to master
Merge pull request #3098 from edx/dcs/paver-watch-assets

Watch for asset changes.
Add in metric tracking to xqueue.

Covers external grading and certificates.
Changed wording for setting up ORA question.
ORA-351
Merge pull request #3100 from edx/waheed/ora351-change-wording-for-setting-up-ora-question

Changed wording for setting up ORA question.
BLD-950: Update captions logic on front-end.
Merge pull request #3128 from edx/anton/transcript-generation

Update captions logic on front-end.