jx_layout_editor: changing partition sizes should be undoable #316

Job	Run time
Build & Package Ubuntu	1h 2m 6s
Build & Package Ubuntu Release	0s
Build & Package MacOS	23m 9s
Build & Package Fedora	17m 32s
Coverage	6m 6s
Upload releases	0s
Update Homebrew Formulas	0s
Build apps (drakon)	3s
Build apps (glove)	2s
Build apps (jx-ide)	3s
Build apps (leibnitz)	2s
Build apps (ssh-askpass)	3s
Build apps (subversion_client)	2s
Build apps (system-g)	2s
	1h 49m 10s

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