Prepare for 0.5.0 release

[uazu]

• Split out QCellOwnerSeq from QCellOwner::fast_new
• Tidy up qcell.rs loose ends
• Polish up docs and examples
• CHANGELOG update
• Scripts for running clippy/doc/tests with all feature combinations
• Update compiletests

[uazu]

@geeklint @steffahn If either of you want to review this patch (or the changes in general since 0.4.3) before I merge this and publish 0.5.0, please do so. I'll leave this up for a few days.

Sorry that this release has taken so long to get done. Covid and/or the vaccines have been messing with my brain and making me less able to get stuff done over the last few months, but I hope that's behind me now. I'll leave the planned TCell/TLCell no_std support for now, to not slow things down any further.

[geeklint]

A scan through and it all looks pretty good to me. One thing, which is maybe more of a nitpick, is the explicit reference to addresses being 2^32 or 2^64; Rust officially supports at least one platform with 16-bit addresses, and is forward compatible with platforms with greater than 64-bit addresses.

[uazu]

Thanks. I want to make it concrete, but I'll change the language to make it clearer and to not exclude other address-widths.

[uazu]

I've published crate version 0.5.0. I will now announce on users and perhaps reddit