Improved HighDPI support by scaling images and sizes

After purchasing a Lenovo Yoga Pro 2, I noticed that FlashDevelop had poor support for HighDPI.

Taking the suggestion of how [Microsoft scaled their images for Visual Studio.](http://blogs.msdn.com/b/visualstudio/archive/2014/03/19/improving-high-dpi-support-for-visual-studio-2013.aspx) I performed similar scaling in FlashDevelop. Updated ImageSize and ImageScalingSize where appropriate. Adjusting Tab rendering to take into account the scaling.

Before
![flashdevelop-4 5 2 scaled](https://f.cloud.github.com/assets/611219/2474999/39fc8804-b052-11e3-937e-e24e098db215.png)

After
![flashdevelop-with hdpi scaled](https://f.cloud.github.com/assets/611219/2475006/5af0c106-b052-11e3-9f23-51a3aacad9af.png)

*Images scaled to 50%

I attempted to be as thorough as possible although it is likely there are still dialogs or controls sized wrongly.