Proposal for DSS-760 - added possibility to define multiple Cryptographic elements with different level attributes in policy file

Created by: nostneji

In https://esig-dss.atlassian.net/browse/DSS-760 the problem is described - there are situations where not only error messages are needed, but the warnings too.

In order to achieve this kind of functionality, the XML-schema dss-policy-jaxb/src/main/resources/xsd/policy.xsd has been changed so that there is possible to define multiple Cryptographic elements with different level attributes. Source files in package eu.europa.esig.jaxb.policy are regenerated. Several files in module validation-policy are changed accordingly. Appropriate unit tests are added.

Also there are some changes in classes ChainItem and CryptographicCheck in order to add algoritm name to error/warning messages.