Data Manager: default pane sizes and user preferences

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Finn commented that when the Data Manager opened up, he always resized the relative sizes of the Tree View and Information panes, increasing the size of the Tree View. He would prefer not to have to do this every time he started Insight.

The relative sizes of each could be a user preference, remembered for future sessions; although Finn's current preference might be due to the current lack of relevant information available in the Information pane - and this might change if/when tag details etc are shown in this panel.