Introduce generic Spinner, use it for messageview

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REVIEW: 112191
SVN_SILENT made messages (.desktop file)
use const references when passing QStrings around

Also "fixes" a trailing newline which was missing.
Add new struct Common::Application with static application values

Trojita code used application name and version strings from QCoreApplication
instance. But this is not correct way if Trojita code is used by another Qt
application (e.g Kontact).

This patch changing Trojita code to use strings from struct Common::Application

Including trojita-version.h in SetCoreApplication.cpp is not needed anymore
because version string is set in Application.cpp

REVIEW: 112121
Merge remote-tracking branch 'pali/pali-application-strings'