view: ensure that width variable is always initialized

Fixes warning: ‘width’ may be used uninitialized in this function.
view: use common infrastructure for remapping obsolete request names

This also removes old remapped names.
Improve configuration error messages
view: move find_enum_map to enum module
view: move prompt toggle lookup to separate method
view: rename toggle option variables
blame: detect file name display on the fly
blame: improve handling of file name visibility
blame: move functionality to colorize ID to draw_id()
view: make options private to each view

This enables options to be toggled individually for each view.
blame: switch to use view_column_draw