turn autoclosePairs and autoNewlinePairs into buffer-local options

[matthias314]

This way one can configure different brackets for different buffers. This seems to me the natural way to do.

At present, the new options are called pairs and newlinePairs. Should the latter one be renamed, for example to newline_pairs?

EDIT: For example, with this PR one can say

micro.InfoBar().Buf.Settings["autoclose.pairs"] = {}

in init.lua's init to turn off autoclosing for the infobar. I don't find that feature helpful when doing incremental searches.