Store and fetch complete view config in and from session config

Summary:
The manual "Dynamic Word Wrap" config key is also the key used by the
generic config for this parameter, so config-backward-compatible change.

Test Plan:
Saving & loading a KDevelop session now restores more of the view settings,
like which borders are shown.

Reviewers: Kate, loh.tar, cullmann, dhaumann

Reviewed By: cullmann

Subscribers: kwrite-devel, kde-frameworks-devel

Tags: Kate, Frameworks

Differential Revision: https://phabricator.kde.org/D27844