configuration within the Swissbib module was extended to use own SOLR RecordDrivers for the swissbib namespace

By now I copied the code from
VuFind\RecordDriver\SolrDefault
VuFind\RecordDriver\SolrMarc
into identical types within the namespace of Swissbib\RecordDriver

it might be a better solution to create a new type which derives from
VuFind\RecordDriver\SolrMarc

todo:
- use the new types for our index (Oliver?)
- get a better understanding of the VuFind Plugin architecture (Guenter)
Creation of a Swissbib/RecordDriver/SbSolrMarc which derives from VuFind/RecordDriver/SolrMarc
Pros:
we can overwrite only the desired methods of the RecordDriver's in the VuFind namespace

possible Cons:
topics for more consideration:
- performance of PHP in case methods are overwritten? -> Snowflake?
- there is another configuration in VuFind\config\module.config.php for VuFind\RecordDriver\SolrMarc
(recorddriver_tabs)
enhancement of the swissbib module configuration necessary?