Something about `Rasterize` which doesn't seem to work as intended.

Recipe:

 1. **Make some simple vector graphics**:

        Test = Graphics[Circle[{0, 0} 1]]

 2. **Try to rasterize** it having defined ImageSize and **ImageResolution**:

        TestNew = Rasterize[Test, "Image", ImageResolution -> 300, ImageSize -> 72]

    `ImageSize` set to 72 means that the resulting image should have exactly 1 inch in size on the screen, since screen resolution is 72 pixels per inch. This is okay.

    `ImageResolution` set 300 means that this image should have dimensions 300 over 300, since `ImageResolution` is defined in printer dots per inch and the image has the size of one inch.

 3. However, **check image dimensions**:

        ImageDimensions[TestNew]

 To discover that it is 72.

Moreover: **the result does not depend at all on `ImageResolution` option**. From documentation: "`RasterSize` and `ImageResolutio`n determine the coarseness of rasterization; `ImageSize` determines the size at which the final image will be displayed." If I vary `RasterSize`, the coarseness indeed changes. If I vary `ImageResolution`, the coarseness stays the same.

**My system**: Ubuntu 14, MMA10.0.1 

**Questions**:  Can anyone reproduce the behaviour? (**done; yes**) If it's not a bug, what is the reason? (**mostly done**: technical reason wonderfully explained by Alexey Popkov) Could someone try this on older MMA versions?


**Edit**: The result I would want to obtain in the above example can be obtained by calling:

    TestNew = Rasterize[Test, "Image", RasterSize -> 300, ImageSize -> 72]

Or, for general image sizes:

    Rasterize[Test, "Image", ImageResolution -> <DESIRED RESOLUTION IN DPI>, ImageSize -> (<DESIRED SIZE IN CENTIMETERS>)*(72/2.54)]

should give the same result as:

    Rasterize[Test, "Image", RasterSize -> (<DESIRED SIZE IN CENTIMETERS>/2.54)*(<DESIRED RESOLUTION IN DPI>), ImageSize -> (<DESIRED SIZE IN CENTIMETERS>)*(72/2.54)]

In other words, `ImageResolution` and `RasterSize` seem to serve the same purpose, but the former one doesn't seem to work as it should.