Changed the "quick config" buttons for the asm config and pseudo-op
tabs into a drop-list and "set" button. The default values for
each assembler are now defined in the Asm*.cs file, rather than in
the settings code.
Rather than have each assembler get its own app config string for
the cross-assembler executable, we now have a collection of per-
assembler config items, of which the executable path name is one
member. The Asm Config tab has an auto-generated pop-up to select
the assembler.
The per-assembler settings block is serialized with the rather
unpleasant JSON-in-JSON approach, but nobody should have to look
at it.
This also adds assembler-specific column widths to the settings
dialog, though they aren't actually used yet.
Each supported assembler has an IGenerator interface and an
IAssembler interface. They're still two separate classes, but now
both are implemented in the same source file. (They'll probably
stay separate classes, since the two have little interaction.)
I'm keeping the "Asm*" filename. Seems the more natural fit.
Also, changed AssemblerInfo to try to get all assembler-specific
stuff into a single table.
