===== DBDriver =====

==== Inheritence Overview ====

  * BaseDBDriver - superclass of all drivers. Some shared utility methods.
    * PipedDrivers - drivers that write and read their data via pipes to external executables. Data is in simple Greenstone archive form (i.e. key/value pairs and separated by seventy hyphens)
      * GDBM - makes use of GDBM utils (txt2db, db2txt etc)
      * GDBMTXTGZ - makes use of gzip (for later use with GDBM)
      * JDBM - makes use of jdbm.jar and JDBMWrapper.jar
      * TDB - makes use of TDB utils (txt2tdb, tdb2txt etc)
    * SQLDrivers - drivers that read/write their data using SQL commands
      * SQLITE - uses calls to SQLite3 via the command line
    * ServerDrivers - drivers that act as clients to externally running servers
      * GDBMS - makes use of a custom GDBM server
      * TDBS - makes use of a custom TDB server
    * MergableDrivers - ???
      * TDBC - ??? Knows how to merge several TDB files into one.