expand_unprintable: use iscntrl rather than isprint which does not work as expected
try to preserve display column rather than buffer column when moving line
DisplayLine no longer map to a single buffer line, but to a buffer range
Try to keep the selection start visible if possible
Add scroll left/right support
pipe: auto insert and end of line if needed
merge AtomContent into DisplayAtom
string escaping support functions

the split function now takes an additional escape parameter and
does not split on separators that have the escaper before it.

An utility escape function that adds escape before separators
is also added.
list,set and tuple options support escaping the separator
go back to : as set/list separator in options
decl command support bool type options
document options in the README
update interfacing.asciidoc
update keymap for case change