generalized monoseq, decseq and incseq; simplified proof for seq_monosub
generalized monoseq, decseq and incseq; simplified proof for seq_monosub

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