Removed R/ prefix from roxygenate dependencies

When Roxygenate runs collate to determine topological sort order of dependencies
It assumes that all files are in the R directory.

Explicitlly adding R/ prefixe in the @include statement throws an error
update_collate adds files R/* to Description
and then roxygenize tries to find them at R/R/*, which do not exist
Added ElasticSearch Reader
use rjdbc database without classpath in config
JDBC connection can use classpath

If claspath was not set, passed NULL into RJDBC adapter.
Now check for NULL and pass instead empty string (the default option)

When no classpath is passed, JDBC uses the loaded classpaths