Update TTLowpassLinkwitzRiley2.cpp

original URL with the article seems outdated, replacing it with a working URL
Update TTLowpassLinkwitzRiley4.cpp

original URL with the article seems outdated, replacing it with a working URL
Don't return activity out message if an error occurs
Merge branch 'dev'
Removing Application attributes reading in TTApplicationManager::ReadFromXml as it is done into TTApplication::ReadFromXml
Adding a mechanism to cache Mirrored attribute in order to avoid network request
Fixing the attribute cache mechanism for Mirror application
Merge branch 'dev' into feature/cmake
Merge branch 'master' into feature/cmake