Improve UBA handling of merges and 18-bit devices

The KS10 UBA was not correctly handing merges of NPR data with PDP-10
memory.

The quick fix that Rob put in a while ago was incomplete.

Also, provide a standard mechanism for 18-bit transfers.
Rework CR emulator to support CD20

The CR device emulation believed that a CD20 was just a CD11.

In fact, it's not.  In addition, a number of problems in the CR and CD
emulations were addressed.

This commit fixes all known problems under TOPS-10, although testing is
on-going.

I don't believe I broke the CR11 emulation, but it needs re-testing.
It's possible that it doesn't have all the fixes, but it shouldn't be
worse than before.

Testing by folks who have 16 and/or 32-bit system disks setup would be
appreciated.

The CR11/CD11/CD20 was completely broken for TOPS-10/20. There was no
emulation of augmented image mode, and timing of error bits was causing
phantom cards to appear regularly. This edit may not be the final
solution, but it passes my test cases on 36-bits, builds and the cli
works on 16 and 32 bits and is a step forward.

Edits included:
Ensure CR doesn't start until set cr reset command is given.
In particular:
attach
enable
bus reset
boot
should not put the cr on-line.

Implement augmented image mode for the CD11, as required
by TOPS-10/20.  Rework CD11 to match hardware.  Make
delays work as intended. Make CD20 a distinct type due
to hardware differences.  Make configuration options
more flexible - and less cluttered for user of a simulator.
Make GO read as zero; cards in motion, move (or jam!). Ensure that
hopper errors are reported with last card to ensure OS
doesn't see phantom cards.
CD11 was not interrupting or clearing GO on card done.
CR11 and CD11 status register and interrupt logic
untangled.  Clearing GO didn't always stop reading.