Admin Guide: split Configuration chapter by section

The Configuration.xml docbook file was nearly 4000 lines, making it
unwieldy to edit.

Each section was moved to a separate file in new subdirectory 'config',
and included in the main file with xi:includes.

The operation was handled using 'dbautosplit' perl script from
http://rpmfind.net/linux/rpm2html/search.php?query=dbautosplit
with some manual adjustments to the generated files.

Fixes #17781
Documentation: improve layout of $g_ldap_server

Use programlisting instead of literallayout
Documentation: improve layout of $g_ldap_simulation_file_path

Use itemizedlist instead of literallayout and add warning para.
HTML/CSS fixes for bug_report_page.php

Added correct class to fieldset to display "required" legend in footer.
CSS: new 'spacer' class for div

In 1.2.x we used to add a table row with a 'spacer' class to separate
rows in a table.

This commit introduces a new class that can be used in form container
divs to separate field container divs:

Before:
	<table>
		<tr>...</tr>
		<tr class="spacer"></tr>
		<tr>...</tr>
	</table>
Now:
	<div class="form-container">
		<div class="field-container">...</div>
		<div class="field-container spacer">...</div>
	</div>
CSS: added new div width classes

With these, we can adjust the layout like it was in 1.2.x tables.
PHPUnit FilterTest failing incorrectly

The test was using a function to returning the 1st 50 issues for all
projects. In a DB containing more than 50 issues, the test would fail
incorrectly.

Now using a filter on the current project only.
PHPUnit HelperTest fix error 4096

Commit 5458f7020999317b35f403fa2a0e477d6182ec12 changed function
helper_array_transpose() signature, the argument MUST be an array so it
does not make sense for the unit test to cover NULL, Scalar and Object
types.
Restore helper_alternate_class() function

This is a temporary measure to improve backwards compatibility of 1.3,
the function will be removed again in the next release.

Fixes #17522 (see also issue #17437)
New DEPRECATED error type

Make use of E_USER_DEPRECATED instead of relying on WARNING for
deprecated functionality. Allows for differentiated error messages and
handling.

Fixes #17837
Add DEPRECATED warning to helper_alternate_class()
Delay printing of deprecated warnings to page bottom

This avoids display errors when a deprecated warning is triggered from
within an HTML tag, as was the case when using helper_alternate_class().
Add link to PHP constants for unhandled error types
Reinstate helper_alternate_class() function

Pull request #234
Add buttons style to table based forms
Localisation updates from https://translatewiki.net.
Login_page.php: Ensure username is valid

This is a fix to improve the behaviour of login_page against possible
XSS exploits to ensure that a username is valid before displaying it
back to the user when entered.

Fixes #17338

Signed-off-by: Damien Regad <dregad@mantisbt.org>