Provide shortcut for getting page header height

Like this, it can be used by multiple components from a single source.
Refactor out page header component

And also tweak some of the properties.
Fix unicode encoding error

Why was that piece of code even there anyway ? :)
Add the SearchField component to Universal Components

When using Silica, it is the Silica SearchField component
and it is currently a normal Textfield with Controls.
Fix background rectangle
Add the TextButton element
Add support for flexible search for the Qt5 GUI
Add the flexible SearchPage component
Add an AddressSearch page

Makes it possible to search for addresses using with the Nominatim online service,
 based on OpenStreetMap data.
Improve debugging a bit
Decode Wikipedia search result as utf-8

Or else JSON parsing will fail duwe to getting bytes
with Python 3.
Add Wikipedia search page

Yes, it is _this_ easy to add another search page.