Make bluecherry icon file name more standard

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>
Renamed .desktop file to conform standards

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>
Better values in debian/control and .desktop files

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>