ViSR: React-grid sizes to fill available window space when controls are open - #169

In Tomography Plots:

• The size of the ReactGridLayout is calculated to use the remaining space after the controls drawer is opened
• --> i.e. when expanded, the controls drawer should show as full sized and the 'plots' should fill the remaining space without needing a scroll bar... until a certain minimum height for the plots is met (at which point a scroll bar appears)
• The slice view now expands to fill the height of the grid, but this has introduced an issue where the width does not resize properly - this is being addressed in ViSR: Make plots size correctly  #164