Check if Scripts have a dialog.

Fixed NonImplementedError when trying to open a config dialogs of
scripts that don't have one.
Fixed Releasetexture. Extended ShaderFilter.

Releasetexture now only releases a texture once.

ShaderFilter can pass settings to shaders.
Updated SuperRes
Merge work
Fix merge
Fix: SuperRes sharpness had the wrong sign.
Center NEDI output
Rework conversions.

Allow a filter to replace itself with another filter. This allows
YuvFilter and RGBFilter to automatically skip processing if possible.
And might also be useful in other filters.

Also replaced the ScaleTo method by a SetSize method which returns
'true' if it succeeded and 'false' if it did not. For the sourceFilter
in the CreateFilter method this will always succeed. Also added an
option to ResizeFilter to use SetSize if possible, and rescale only
if this fails. Since this can affect the inputFilter it should be
used carefully.
Merge pull request #26 from Shiandow/master

Update SuperRes. Various changes to Filter.cs. Fixed script dialogs in Script Chain.