Therion 0.2.17

[Martin Budaj]

Good news for all MetaPost fans!
Therion 0.2.17 supports
* easy switching among predefined map symbol sets
 (symbol-set, symbol-assign, symbol-hide options of the
 layout command)
* customized map symbols loaded in the run-time
 (new symbols may be defined inside of 'code metapost' section
 of the layout command)
 There is no need to recompile Therion when new symbols are added.
* optical map scaling (base-scale option)
Regards,
Martin