MDL-47143 questions: fix default for question_preview/marks setting.
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-46195 fix error handling.
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-47187 assign: fixed timing unittest failure
MDL-46844 Embed LTI External Tools with an IFrame

Clears up weird browser issues that occur when embedding content with an
`<object>` tag.
MDL-47209 repository_skydrive: Use new oauth URLs
MDL-46747 questions: add More info link to qbehaviour help.

Thanks to Tony Gardner-Medwin for the suggestion.
MDL-46588 web services: Fixed invalid check of empty contextid in function get_context_from_params
MDL-46588 web services: Unit tests added
MDL-46588 web services: Fixed system context instanceid eq 0 case
Merge branch 'MDL-47209-26' of git://github.com/FMCorz/moodle into MOODLE_26_STABLE
Merge branch 'MDL-46747_26' of git://github.com/timhunt/moodle into MOODLE_26_STABLE
Merge branch 'MDL-46944-26-lti-iframe' of git://github.com/schmod/moodle into MOODLE_26_STABLE
MDL-47167 XML question format: behat tests
Merge branch 'MDL-47143_26' of git://github.com/timhunt/moodle into MOODLE_26_STABLE
Merge branch 'wip-MDL-47187-m26' of git://github.com/marinaglancy/moodle into MOODLE_26_STABLE
Merge branch 'MDL-46331_26' of git://github.com/timhunt/moodle into MOODLE_26_STABLE
Merge branch 'MDL-46195_26' of git://github.com/timhunt/moodle into MOODLE_26_STABLE
Merge branch 'MDL-46588-26' of git://github.com/jleyva/moodle into MOODLE_26_STABLE