Remove useless forward declaration

Change-Id: I59de95d2d2e72b676df50ede6c9d3c6182b38892
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
WelcomePage: Support additional (non-qt) example sets

Added with setting "Help/InstalledExamples" which is a string list, each
string is a triple of (display name, manifest parse path, examples
path), joined with '|'.
If a documentationPath for a Qt version is already added through the
InstalledExamples setting, we do not show an extra combo box item for
it. That makes it possible for an installer to register a single example
set for the same Qt version in different variants (e.g. iOS, Android
x86, Android arm)

Change-Id: I42dd8f9ca9cb6cee247e3dc8ce9d014e56852e79
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Examples: Move example combo box to the left

That makes it more visible, which is especially important when we show
example sets that do not come from a Qt version there.

Change-Id: Ib99955e70abb95053d9e8cd718ab599153e6eaaf
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>