Cmobase v0.6

[dkruckemyer-ventana]

Incorporated feedback from architecture review. Functional changes:

• Added virtual instruction exception conditions
• Added constraints on PMAs and PMP access control bits for cache blocks
• Added new supported access type PMA for cache-block zero accesses
• Fixed bugs in the pseudo-code for determining illegal instruction and virtual instruction exceptions
• Various clarifications and editorial changes requested by the reviewers
• CSRs are WARL, per request