Bug 30135: Add EdifactLSQ mapping preference

Bug 30135: Add EdifactLSQ mapping preference

This patch adds a new system preference, EdifactLSQ, to allow
configuration of the ambiguous LSQ, sequence code, field included in the
EDIFACT specifications.

Originally the field was hard coded to map to 'location', but as per the
specification it could have been mapped to 'ccode'.

From the specification:

A code or other designation which identifies stock which is to be
shelved in a specified sequence or collection.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>