Add Wbmp & Otb Encoding / Decoding

[reshane]

Related to Issue #1

Switched the image patch to my own fork to add the Wbmp & Otb formats to the image::ImageFormat enum so the hooks would register. Not exactly sure the best course of action to add the formats - whether to open a PR for the formats now, wait for the decoding-hooks branch to be merged, etc. guidance appreciated 😃

Note that OTA Bitmap Wikipedia article differs from ImageMagick implementation for the format (ImageMagick splits rows at bytes - padding with 0s, while Wikipedia explicitly claims this is not the case). (OTA Bitmap Wiki, ImageMagick implementation)
I have gone with an implementation consistent with ImageMagick, but the implementation consistent with the Wikipedia is easier, so if there is any evidence that the latter is valid I would be happy to switch it back.

I had some trouble finding otb / wbmp images with explicit licenses, so I drew the test images which is why there is no source listed for them.

[mstoeckl]

Not exactly sure the best course of action to add the formats - whether to open a PR for the formats now, wait for the decoding-hooks branch to be merged, etc. guidance appreciated 😃

The main image crate has recently had a release (0.25.8) adding a decoding hooks API.

I have gone with an implementation consistent with ImageMagick, but the implementation consistent with the Wikipedia is easier, so if there is any evidence that the latter is valid I would be happy to switch it back.

I think Wikipedia is right. Quoting the Smart Messaging Specification 3.0.0 (linked from https://web.archive.org/web/20161016190953/http://fileformats.archiveteam.org/wiki/OTA_bitmap), Section 3.7:

In order to fully utilise the available bandwidth no filler bits are used in the end of the row; fillers are put at the end of the whole bitmap if the size of the bitmap is not divisible by eight. Filler bits assume a value of zero.

Also, WBMP and OTB look like they are quite rare formats nowadays; if you don't mind me asking, what are you decoding and encoding them for?