Port cirkuit's main.cpp to KF5

Summary:
The following deprecated classes are ported to their Qt/KF5 counterparts:

• KApplication -> QApplication
• K4AboutData -> KAboutData
• KCmdLinArgs -> QCommandLineParser

Translation now uses i18n(str) from KLocalizedString instead of ki18n(str).

Strings for the commandline parser are adjusted to fit current
kde scheme:

• '+' removed from argument syntax
• '.' added at the end of the argument description

The string parameter shortDescription passed to K(4)AboutData got
split up into shortDescription and otherText.
The html markup contained in this param looked really ugly in the
commandline output.
Now only the short markup-free text is displayed on the commandline,
while in the about dialog (visually) nothing has changed.

Reviewers: asturmlechner

Reviewed By: asturmlechner

Differential Revision: https://phabricator.kde.org/D10999