Feature Request: Remember docked dialog dimensions

Migrated from: https://bugs.launchpad.net/inkscape/+bug/1776176

Steps to reproduce:

• Open Inkscape with any dialog(s) open and docked.
• Drag dialogs to make the dock larger
• Restart.

What happened?

Dock width is not remembered.

Docked dialog dimensions are not remembered.

Inkscape Version and Operating System:

• 1.0alpha master, Linux Mint 19.1
• 0.91 r13725 on Ubuntu 16.04.

Before restart	After restart