Add Support for `mov rx,<immed>`

This release adds support for the mov rx,<immed> instruction. Several bug fixes were also included to address the organization and byte order handling for the code.

Additionally, an update to the architecture definition language was made to allow for the organization to drive the constant output into the instruction stream. A new definition is allowed in the following form:

.opcode         mov    r1,$(16)     .mc 0013 %

... where the $(16) indicates the size of the constant (no change from before) and % is used to show the placement of that constant, but use the rules set forth in the architecture to order the constant bytes.

.mc ("Machine Code") replaces .db for the output definition where the output will be organized consistent with the architecture's organization. .db is slated to be removed and for now any instance of .db is assumed to be .mc.