QML template needs to be updated due to the new feature in the header

[XiaoGuo, Liu]

Whenever we create a new template app, we run it, and it complains that:

QML debugging is enabled. Only use this in a safe environment.
Loading module: 'libubuntu_application_api_touch_mirclient.so.3.0.0'
qml: Page_QMLTYPE_9(0xb8d0a8)"labelbase": In Ubuntu.Components 1.3, the use of Page.title, Page.flickable and Page.head is deprecated. Use Page.header and the PageHeader component instead.
ubuntumirclient: Got invalid serialized mime data. Ignoring it.

We need to update our template app according to https://developer.ubuntu.com/en/blog/2016/02/24/pageheader-tutorial/ accordingly.

Best regards,
XiaoGuo