Support ICC colorspace

[gunnsth]

Implement a package to interpret and utilize ICC based colorspaces.

See section 8.6.5.5 ICCBased Colour Spaces (PDF32000_2008):

ICCBased colour spaces shall be based on a cross-platform colour profile as defined by the
International Color Consortium (ICC)... an ICCBased colour space shall be characterized by
a sequence of bytes in a standard format. Details of the profile format can be found in the
ICC specification.

There are multiple versions of the ICC specification that are supported in PDF as shown in Table 67 (PDF32000_2008). However, it also says that

• A conforming reader shall support ICC.1:2004:10 as required by PDF 1.7, which will enable it to properly render all embedded ICC profiles regardless of PDF version.
• Thus it should be enough to support that version or newer if it exists.

Notes

• Should be designed such that it can be used within unidoc for image processing
• The current implementation uses the alternative colorspaces that are provided, so this will be a good improvement for color handling.

[gunnsth]

We need examples of how this would be used, what example API usage could look like, etc. Both for decoding and encoding applications.