Bug 6537 - squashed version of the previous 5 commits, signed-off

Bug 6537 - squashed version of the previous 5 commits, signed-off

Bug 6537 - Move installer/data/mysql/en/mandatory/sysprefs.sql to installer/data/mysql/sysprefs.sql

Bug 6537 - Make the web installer use installer/data/mysql/sysprefs.sql

Bug 6537 - New syspref files with only the prefs that differ from the default

I have mostly deleted old syspref files and created new ones, with a new name,
mainly in order to reduce the risk of merge conflicts if the old syspref files
are changed before this patch is pushed, if it is pushed.

See http://wiki.koha-community.org/wiki/Simplified_syspref_handling_RFC for
a description of how the new files were created to reflect sysprefs that
differ from the global default.

.txt files have been moved to reflect the new names of the SQL files they are
associated with.

Bug 6537 - Remove syspref-related tests in xt/

As far as I can see, the previous patches for this bug makes the syspref tests
obsolete, and this patch removes them:

xt/syspref.t
xt/check_sysprefs.t

Bug 6537 - Fix a problem in French syspref file

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>