Numerous tweaks, responding to Marc Gauthier (#463)

* Numerous tweaks, responding to Marc Gauthier

See https://lists.riscv.org/g/tech-debug/message/755



* Rename W to WARZ.

* W1 fields should read 0.

* Rephrase hartinfo.dataaccess.

* Abstract reg access may fail depending on state.

* Register increment may not happen when transfer=0.

* Clarify writing command while busy=1.

* may is ambiguous, might is unambigous

Co-Authored-By: Paul Donahue <48959409+pdonahue-ventana@users.noreply.github.com>

* Rephrase behavior when writing command while busy.

* Update same sentence everywhere.