Add a movement code (e.g., SBL) to movement table

[ssmith55]

Movements are currently identified either by
mvmt_id - a unique key for the table
combination of ib_link_id and type (e.g., left)

The request is to add a field, mvmt_txt_id (e.g., SBL for southbound left). This field, when combined with the node_id, would provide a third unique identifier, and will match common practice in other applications, such as Synchro.

Proposed syntax would be DDTN, where DD is the direction (e.g., SB, NB, EB, WB, NE, NW, SE, SW). T is the turning movement (e.g., R, L, T) and N is an optional turning movement number (e.g., distinguishing between bearing right and a sharp right at a 6-way intersection)