Update README.md
Made utility class Resources unconstructable.
Added an attributes system similar to the resources system, closes #129.
Added method to sanitize tag input.
The XmlCardLoader now sanitizes the input when reading resources from cards, closes #133.
The XmlCardLoader will now check the input ECSResources to make sure there is no sanitized name conflict.
Renamed occurences of resource related terms to attribute related terms.
Merge branch 'issue129-ecs-attributes' of https://github.com/Cardshifter/Cardshifter into issue133-cardloader-case
Added initial support for attributes in the card loader.
Added default methods to ECSResource and ECSAttribute to obtain that resource or attributes value from an entity.
Added javadoc to the getFor default method of ECSResource and ECSAttribute.
Fixed bug where a NPE could occur if ECSAttributeData was working with null elements.
The <Name>, <Image> and <CardType> tags are no longer mandatory on cards, instead an <Id> tag is now mandatory.
Fixed bug where a NPE could occur if ECSAttributeData was working with null elements.
Disallowed different cards having the same id.
A bug has been solved where inputting an integer value in an attribute field would cause the field to be treated as a resource.
Added card id to the exception message when an error occured in the card loader.
Merge branch 'issue129-ecs-attributes' of github.com:Cardshifter/Cardshifter into client-server
Merge branch 'javafx' of github.com:Cardshifter/Cardshifter into client-server
Added extra tests to verify that attributes are properly supported in the card loader, closes #130.