MDL-46195 Fix fractionsaddwrong string component in lesson & qformat_webct.

I know. You should not refer to strings from other plugins, but

* qformat_webct is importing multichoice questions in that bit of code.
  I suppose a pedant would say that qformat_webct should declare dependencies
  on all the qtypes it relies on, but that would be silly.

* Lesson should be using the question engine, rather than doing its own thing.
MDL-47143 questions: fix default for question_preview/marks setting.
MDL-46810 question CBM behaviours: improve the display of marks.

Thanks to Tony Gardner-Medwin for the suggestion.
MDL-47127 gradereport_user: Update 'datetill' string to make it more clear
MDL-46195 fix error handling.
MDL-46811 update download.moodle.org url to https

https is now the prefferd protocol for this site
Automatically generated installer lang files
MDL-46195 WebCT question import: Behat test
MDL-47167 XML question format: behat tests
MDL-46331 GIFT question import was breaking content inside <pre>.

Also, adding a Behat tests to verify GIFT import works without errors
(but leaving the detailed testing for the unit tests).
MDL-47186 calendar: Changed month name to h2 from h1
MDL-47187 assign: fixed timing unittest failure
MDL-46834 dndupload: check course dndupload cap on course level
MDL-46572 behat: Select user dialogue is not visible in phantomjs
MDL-46844 Embed LTI External Tools with an IFrame

Clears up weird browser issues that occur when embedding content with an
`<object>` tag.
Automatically generated installer lang files
Revert "Merge branch 'wip-MDL-40356-master' of git://github.com/abgreeve/moodle"

This reverts commit 4b5fd6eb6d34b5c519d778a8d9c5c1a014146f54, reversing
changes made to a788aade7ce694b3f36c8e27295c60a5178c5b23.
MDL-46834 dndupload: check course dndupload cap on course level
MDL-47209 repository_skydrive: Use new oauth URLs
Merge branch 'install_master' of https://git.in.moodle.com/amosbot/moodle-install