Inspector: Add new AdvancedSlider control

[EchterAgo]

Replace the old RangeEditor and TextBox numeric editors with the new
advanced slider control. The user can use a combination of ALT, CTRL and
SHIFT keys to adjust the rate of change. The user can also double click
the value to edit the value numerically.

Signed-off-by: Axel Gembe axel@gembe.net

This needs #193 merged first.

[EchterAgo]

This is a large one. Sadly it can not be used with nullable values.

[EchterAgo]

These should maybe come from an attribute as well.

[EchterAgo]

Rebased on top of #192

[EchterAgo]

Updated patch to make it easier to set the cursor inside the text field and to make the text box use the key down event for ending editing so that other controls do not handle the key down event first.

[EchterAgo]

Updated to support keyboard focus

[tgjones]

This looks quite nice. I'm concerned about the overlap with NumericTextBox though (as seen in the MonoGame demo, in the Vector3 property editor). Could we extend NumericTextBox instead of introducting a new control?

In any case, I'll wait till #192 is merged, so that the diff here is easier to review.

[EchterAgo]

Rebased

[tgjones]

Please could you rebase this again?

[EchterAgo]

I'll do that, but I'd like to look into addressing your concerns regarding NumericTextBox overlap first. I think you should take a look at merging #298, it is a simple bugfix.