MDL-37459 admin: Set the default setting flags on a new install.

Make sure the default flags for all settings are saved on a new install.
Revert "MDL-39832 Files: Fixed ETag format according with RFC2616."

This reverts commit 9ab37ae3e07f54bc08644f8462d94bed68ff6c9b.
Revert "MDL-39832 Files: Revert MDL-39688 commit, f111746140fe80a821ae69e3bf518d950bf188a1"

This reverts commit 3960c00e3cf129c60b01fecdfe2851ba9ef7ba59.
MDL-38851 javascript: Full screen dialogs on small screens

This change adds support to M.core.dialogue for showing fullscreen
dialogs on small screen sizes. There are 2 new configuration values that
can be set to control this when creating a dialog (responsive and responsiveWidth).

Setting responsive to false will disable this functionality completely (old behaviour).
Setting responsiveWidth controls the screen width that the dialog will switch to
fullscreen mode. Try not to think of the device that will be accessing the dialog,
but the width at which the content of the dialog needs to be displayed differently.

The activity chooser and the filepicker are the two dialogs that have been converted
in this patch. The filepicker first had to be converted to use M.core.dialog and not
Y.Panel.