Added simple diagnostics

include/dusk/AST/ASTDiagnostic.h

include/dusk/AST/ASTVisitor.h

include/dusk/AST/CMakeLists.txt

include/dusk/AST/Decl.h

include/dusk/AST/Diagnostics.h

include/dusk/AST/Stmt.h

include/dusk/Frontend/Compiler.h

include/dusk/Frontend/Formatter.h

include/dusk/IRGen/CMakeLists.txt

include/dusk/IRGen/IRGenerator.h

include/dusk/Parse/Lexer.h

include/dusk/Parse/Parser.h

include/dusk/Parse/ParserResult.h

include/dusk/Parse/Token.h

lib/AST/ASTPrinter.cpp

lib/AST/ASTWalker.cpp

lib/AST/CMakeLists.txt

lib/AST/Decl.cpp

lib/AST/Diagnostics.cpp

lib/AST/Expr.cpp