Rename Descale props

[LightArrowsEXE]

For clarity purposes (and so I can support them in Jaded-Encoding-Thaumaturgy/vs-preview#182 without fear of it overlapping with other random props), it may be a good idea to prefix these props with "DT" or otherwise rename them to make it clear these are properties from your descaling classes.

vodesfunc/vodesfunc/rescale_ext/mixed_rescale.py

Lines 42 to 44 in b87c906

	self.descaled = self.descaled.std.SetFrameProp("Target", self.index)
	self.rescaled = self.rescaled.std.SetFrameProp("Target", self.index)
	self.upscaled = self.upscaled.std.SetFrameProp("Target", self.index)

vodesfunc/vodesfunc/descale.py

Line 105 in b87c906

self.input_clip = clip.std.SetFrameProp("Target", self.index + 1)

Note that the official Vapoursynth documentation recommends using CamelCase for frame properties.