Revert "added commandline options for modification time sync"

This reverts commit c65c2b8a1a791cb2aedeb523a830872b4e4d603d.
Revert "made INTERNALDATE and mtime sync support optional"

This reverts commit 68d3c16f75b17ea43444213e06fb4abeea9448f7.
added KeepModificationTime yes|no option for channels