Add support for OS Features in the format

[dmcgowan]

Updates the os part of the format to include features after the os version. The guarantees that the format may fully represent the platform structure.

I propose we consider including the features in the format for 1.0 release, which we are trying to finalize.

Should we consider "/" or "+" as supported parts of OS features here? Right now the spec does not specify but we can define our own limitations. We could support it either by updating the parser (less backwards compatible) or URL encoding (ugly, but could be an edge case so who cares).

[tianon]

Does the format already support (non-OS) features?

(I don't think either are currently used for anything serious, but if we're going to support one we should probably support the other too.)

[dmcgowan]

Does the format already support (non-OS) features?

Which format are you referring to?

In OCI there are non-OS features reserved, but not sure if that will ever be defined or added to the struct. I don't know where the line would be drawn in this case in regards to OS feature vs non-OS feature. It could be a hardware feature stuffed in as an OS feature, but what really is the difference if any hardware feature ends up being visible through the OS anyway. This is more for completeness of avoid compatibility later on when we want to add it, as had been previously discussed and recently inquired about.