formatting: don't use smartindent
initial work on context sensitive autoformat feature
formatting: improve smart autoformatting.
formatting: improvements for autoformatting of lineblocks and blockquotes
formatting: improvements to autoformatting of lists and blockquotes.
doc: document smart autoformatting features.
formatting: smart autoformatting should ignore YAML stuff.
formatting: don't use 'w' in formatoptions, in messes up lists.
Wrap cursor around line boundaries by default

implements issue #86.
adding 'spell' module.
spell: set settings locally.
add more syntax groups to default blacklist

fixes issue #91.
pandoc/keyboard/sections: count line width taking multi-byte characters into account

fixes issue #90.
doc: fix minot typo
folding: add 'stacked' mode, and a command to change folding mode on demand

Implements idea fro issue #89.
formatting: update formatoptions only when lnum changes or in InsertEnter.
Rip out most of the code and initial method definitions.