silvia_manager: added support for deleting credentials
silvia_issuer: explicitly asks for the credential PIN
silvia_irma_manager.cpp
Merge pull request #22 from adelapie/master

Added support for deleting credentials
silvia_manager: Fixed comment
silvia_manager: now outputs the removed credential
silviar_manager: Added support for updating the credential pin
silvia_manager: Added support for reading the attributes of a given credential
silvia_manager: Fixed typo
Improved documentation/added tutorial
Updated README.md
Added corrections to README.md
Merge pull request #23 from adelapie/master

silvia_manager: Fixed comment