Bug 16573: fix structure and sample data for MySQL 5.7

Bug 16573: fix structure and sample data for MySQL 5.7

Web install on Ubuntu 16.04/Mysql 5.7 fails.

This patch makes small changes to make installation
possible to kohastructure.sql and some sample files.

Sample values for quotes table can't have '0000-00-00 ...' values
nor NULL values, now() is perhaps an option.

Depends on Bug 16572

To test:
1) System with MySQL 5.7, for example Ubuntu 16.05
2) Apply 16572
3) Try web install, it fails
4) Apply this and next patch
5) Try again, now it succeed

This is only for English install, i18n files needs revision
I can do that if this is accepted.

Perphaps a change is needed to updatedatabase.pl

Ammended patch, 'created_on' field on virtualshelves
can't be timestamp default null, mysql 5.5 complains
that only one timestamp column can be defined as
default not null. Changed to 'datetime' type.

Can provide followup with updatedabase change,
but need an opinion if this type change makes sense.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>