Merge branch '39-add-frontend-for-rules' into 'dev'

eraser-base/src/main/jastadd/Expression.relast

eraser-base/src/main/jastadd/Printing.jrag

eraser-base/src/main/jastadd/Resolving.jrag

eraser-base/src/main/jastadd/Rules.jrag

eraser-base/src/main/jastadd/Rules.relast

eraser-base/src/main/jastadd/eraser.flex

eraser-base/src/main/jastadd/eraser.parser

eraser-base/src/main/jastadd/shem.jrag

...n/java/de/tudresden/inf/st/eraser/util/MemberPrinter.java

...e/src/test/java/de/tudresden/inf/st/eraser/RulesTest.java

eraser-base/src/test/resources/tests/ppc2/input.eraser

eraser-base/src/test/resources/tests/ppc2/output.eraser

eraser-base/src/test/resources/tests/ppc6/Test.properties

eraser-base/src/test/resources/tests/ppc6/description

eraser-base/src/test/resources/tests/ppc6/input.eraser

eraser-base/src/test/resources/tests/ppc6/output.eraser

pages/docs/DSL.md