Consider adding format specific defaults

[mwestphal]

Currrently, all our options default are perfectly static, while this is in line with F3D minimalism, some formats have inherent information related to the format that we should account for in our defaults, thus having "format specific defaults"

These "format specific defaults" should be:

• Specific to the F3DReader associated to the format, not the file
• Do not cause any kind of delay in opening the file.

I have look through the options and I think the following may be to be considered for "format specific defaults":

• --up: Some formats are expected +Y, other are +Z
• --animation-index: Some formats are expecting to enable all animations, while on some format it does not make sense/not supported, so enabling the first animation would make sense
• --point-sprites: some format could be specialized for point clouds, then setting this would make sense, no formats yet

In terms of implementation, this would means the F3DReader contains accessor to these default and reader needing to set it implement them, quite easy. It also means we need to document the format specific defaults.

[mwestphal]

This would come into consideration with #49 @Meakk @jpouderoux

[mwestphal]

With the recent improvements to config file, this feel not necessary anymore.