add getCompiler and getLinker methods, to abstract from XSD.
add calc_source_md5 as it's more convenient especially for embedded
targets to add -DPLC_MD5="something" option at compile time than
to mess with editing binary.
add some more helper methods

<?xml version="1.0" encoding="UTF-8"?>
<BaseParams Name="py_ext_0" IEC_Channel="0"/>