Bug 17942 - Update style of the web installer with Bootstrap 3

Bug 17942 - Update style of the web installer with Bootstrap 3

This patch makes style and markup changes to the web installer and new
onboarding tool (Bug 17855).

- Markup has been corrected, improved, and in many places reindented.
- Some page titles have been made more specific.
- Some JavaScript and CSS have been moved to separate files.

In the onboarding tool I have removed form validation from the markup
and JavaScript in many cases where the requirements were not matched
elsewhere in Koha. For instance, we shouldn't limit item type
descriptions to only letters because the database doesn't require such a
limit.

To test, apply the patch and run the web installer with an empty
database. Confirm that the installation process completes correctly and
that each page looks good and works correctly.

Works as advertised
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>