Exclude X-FESS Metadata from Indexing and Add Metadata Transformation Process

[marevol]

We need to make two key changes to our current system:

1. Exclude metadata starting with "X-FESS" from the indexing process.
2. Add a transformation process to include metadata for indexing.

The changes involve modifications to AbstractFessFileTransformer.java, FessConfig.java, FessProp.java, and fess_config.properties. Specifically, we have:

• Added X-FESS.* to the list of excluded metadata in the indexing configuration.
• Introduced a method to add new metadata mappings for indexing transformation in FessProp.java.

This will enhance our metadata handling and ensure that certain metadata is appropriately excluded from indexing while allowing for dynamic addition of new metadata mappings.