support for floats, mouse wheel rotation, plugin settings, preset sizes, edit boxes in toolbar and attributes for created geometry.

[Tirpitz93]

I have taken your plugin and made what I believe are some usability improvements. Please feel free to look over them and merge if you feel they have merit.

• Now support floats instead of integers.
• Now used the mouse wheel to rotate the rectangle if shift is held.
• stores plugin settings with QgsSettings
• Adds preset sizes and ability to save your own presets with labels.
• adds 3 edit boxes to the toolbar for quicker adjusting of sizes.
• saves attributes to the layer if the fields rotation, width, height are present in the layer, (any combination can be omitted).
• Catches python exceptions to prevent QGIS crashes.