Enable/disable the width, height and table widgets based cross section shape

[leendertvanwolfswinkel]

Depending on the selected shape, some widgets (and their labels and X buttons) should be enabled / disabled. The following list shows the widgets that should be enabled for each shape:

• None: None
• Circle: Width. Change name of the label to "Diameter [m]"
• Egg: Width.
• Open rectangle: Width
• Closed rectangle: Width, Height
• Tabulated rectangle: Table
• Tabulated trapezium: Table

This applies to the layers Weir, Orifice, Culvert, Pipe and Cross section location

[leendertvanwolfswinkel]

@ldebek I changed the ticket to match the new Open rectangle / Closed rectangle categories

[ldebek]

Fix available at branch: issue_78_fix

[leendertvanwolfswinkel]

@ldebek Perfect, please merge