add lemma norm_diff_ineq; shorten other proofs
add lemma norm_diff_ineq; shorten other proofs

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle