Re #8472 - Made small fixes to the CertificateRepository
Re #8471 - Merge implement DAO - source code
Re #8471 - Implemented filter of certificates- Implemented filter by certificate type using index (id) from CertificateTypes table- No multiple types supported
Re #8471 - Error correction after review
Re #8471 - Simplification of CRUD functions- conversion source of certificate repository to one file- added comments
Re #8471 - Modified source- deleted redundat files- deleted '_impl' from repositories filename