Update documentation to spring-data

[hohwille]

Currently the JPA Guide is strongly tied to the DAO approach: https://github.com/oasp-forge/oasp4j-wiki/wiki/guide-jpa

With PR #626 we now have advanced spring-data support and it becomes first class citizen. This implies the following tasks for documentation improvements:

• [x] extract DAO alternative from JPA guide to new separate page
• [x] change JPA guide to spring-data usage
• [x] add link to new DAO alternative from JPA guide as alternative to spring-data with rational to use in contexts where strict JEE is required or spring should be decoupled as much as possible.

[hohwille]

• https://github.com/oasp-forge/oasp4j-wiki/wiki/guide-jpa
• https://github.com/oasp-forge/oasp4j-wiki/wiki/guide-repository
• https://github.com/oasp-forge/oasp4j-wiki/wiki/guide-dao
• https://github.com/oasp-forge/oasp4j-wiki/wiki/guide-jpa-query
• https://github.com/oasp-forge/oasp4j-wiki/wiki/guide-jpa-performance
• https://github.com/oasp-forge/oasp4j-wiki/wiki/OASP4J