Add changes list for SVN commit dialog

Summary:
SVN commit dialog box contains no list of changes that will be commited. This is often confusing.
This commit adds basic changes list for SVN commit action.
Also contains workaround for QTBUG-40584 to preserve dialog sizes, see KWindowConfig::restoreWindowSize() docs.
{F7948018}

Reviewers: #dolphin, elvisangelaccio, meven, #vdg, ngraham

Reviewed By: #dolphin, meven, #vdg, ngraham

Subscribers: ngraham

Differential Revision: https://phabricator.kde.org/D26921