[cosmetics] update copyright headers
Merge pull request #3002 from MartijnKaijser/update_header

update copyright headers
Remove misrepresented parameter from IAddon::Clone(), CAddon::CAddon(const CAddon&) and related subclass methods
Move member initializers from CRepository::Clone() to copy constructor.

Also adds missing m_hashes member.
Move CScreensaver cloning to new method, CScreensaver::Clone()

CScreensaver::Clone() is virtual and overrides IAddon::Clone()
Remove unused member variable AddonProps::parent
Remove IAddon::Path() and replace with simple flag in CAddonDLL