Pagecontainer: Document that external widgets must also be copied

When navigating between HTML documents with Ajax and pushState, every one of
those documents must contain copies not only of the header scripts, but also of
the widgets that are external to pages, but shared between them.

Closes gh-305
Fixes gh-304
1.4.8
Navigate: Fixed error in warning text

Fixes gh-289
Closes gh-290
Pagecontainer: Update events and deprecations for 1.4.3

Closes gh-297
Panel: Fixed typo in panel class name
Build: Update license

Closes gh-309
1.4.9
1.4.10
All: Updated jQuery Mobile version to 1.4.3
Closes gh-321
1.4.11
Pagecontainer: Changed default value for showLoadMsg
Fixes gh-241
Closes gh-325
Popup: Add note for popups with a header and a closing button
Closes gh-327
1.4.12
Build: Upgrade to grunt-jquery-content 0.12.0
1.4.13
Build: Upgrade to grunt-wordpress 1.1.0 and grunt-jquery-content 0.12.1
1.4.14
Build: Upgrade to grunt-wordpress 1.2.1 and grunt-jquery-content 0.13.0
1.4.15
All: Updated jQuery Mobile version to 1.4.4
Closes gh-335