This change moves 'Extending QML' qdoc file and the tutorials
from examples/quick to examples/qml, which is the correct
location for them.

Change-Id: I24bd9dfa75baaab7bc8efe08489f09a7b65d98a6
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>
Reviewed-by: Alan Alpert <aalpert@blackberry.com>

-"element" -> "type" or "object" (not in all cases where this change applies)
-some instances of QtQuick. It should be "Qt Quick".
-only in qdoc files. Examples and source code changes will be done later.

Task-number: QTBUG-30180
Change-Id: Ie587461a138e97606f761ad1e90909c91b479303
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Reviewed-by: Martin Smith <martin.smith@digia.com>

Task-number: QTBUG-30233
Change-Id: Ic0a6d9112dbf8903d68f571e0ac853d89ff31ebe
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>

Task-number: QTBUG-28756

Spurious repetition of the definite article

Doc: corrected trailing space issue.

Change-Id: I95c1c5773dc4b25dd0a3625343a67975783435fd
Reviewed-by: Geir Vattekar <geir.vattekar@digia.com>

Change-Id: I6c3bd7bebe3d62d1cfd0fa6334544c9db8398c76
Reviewed-by: Akseli Salovaara <akseli.salovaara@digia.com>
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>

Snippets are fixed, the extending-examples are moved from
QtDoc, groups are used to generate the lists and I've removed
some unrelated stuff from the list of Qt Quick examples.

Change-Id: I347b6fa8a29b1cede1164fa858488f34507e1a17
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>