remove preprocessor from main repo and add it as a submodule

.gitlab-ci.yml

.gitmodules

relast.preprocessor

relast.preprocessor/.gitignore

relast.preprocessor/build.gradle

relast.preprocessor/src/main/jastadd/Analysis.jrag

relast.preprocessor/src/main/jastadd/DumpTree.jrag

relast.preprocessor/src/main/jastadd/NameResolution.jrag

relast.preprocessor/src/main/jastadd/Navigation.jrag

relast.preprocessor/src/main/jastadd/Preamble.parser

relast.preprocessor/src/main/jastadd/RelAst.flex

relast.preprocessor/src/main/jastadd/RelAst.parser

relast.preprocessor/src/main/jastadd/RelAst.relast

...reprocessor/src/main/jastadd/backend/AbstractGrammar.jadd

...r/src/main/java/org/jastadd/relast/compiler/Compiler.java

...ssor/src/main/java/org/jastadd/relast/compiler/Utils.java

...java/org/jastadd/relast/compiler/options/CommandLine.java

.../java/org/jastadd/relast/compiler/options/EnumOption.java

.../java/org/jastadd/relast/compiler/options/FlagOption.java

...main/java/org/jastadd/relast/compiler/options/Option.java