* Deprecate upper & lower option.
These does not make much sense and `format` option can provide same results
* Unify padding options
* Add persistent notices
* Make separators use left/right keys to specify left right instead of
sequence
* Rename format -> fmt
* Rename condition -> cond
* Rename disable_text -> icon_only
* Unify color_error,warning,info,hint under diagnostics_color
* Unify color_added,modified,removed hint under diff_color
- Now all color related options and themes color definition have same
semantics. They can either be a table containing values like bg,fg,gui
or a string. When it's a string it's treated as a highlight group name
and newly created group is linked to that group.
- Using string values to define foreground colors in options like
color_error/color_added in diagnostics and diff component has been
deprecated.
- Added a decent way of notifying affected users of deprecations and
breaking changes.