remove ModelDescription from Feature, saving 152 bytes per Feature, i.e. 44%
removed dependent classes which were deprecated before
[DOC] renamed README to README.md to enable rendering as markdown on github
[DOC] improved documentation for external projects
missing model tag in featureXML is non-fatal, fixed tests
Merge pull request #1011 from aiche/fix/external-project-doc

[FIX] external project doc
deleted SimpleSeeder and SimpleExtender as well
Merge pull request #1012 from cbielow/fix/feature_class_size

[FEATURE] decreased memory footprint of Feature class by up to 44 percent