Fixes #8207 mantis_project_hierarchy_table allows duplicate rows

This fixes a possible issue where the project hierarchy table can contain duplicate entries, by adding a unique index on the table
Document ability to display status on bug_report_page.php

Fix for issue #14678 omitted to amend the comment block in
config_defaults_inc.php as well as the documentation.

Fixes #17289
Fix query execution error in user_get_accessible_subprojects()

Because of missing '!' operator, the parameters array did not have
enough values for the query when $p_show_disabled = true.

Regression introduced by 927706b3311407712ee16b9be71f56a974683d73
Tweak messages
Fix i18n issue in login_page.php

Sentence parts should now be glued together. Instead, I've created full
sentences. They are combined using a word separator.
Use "code" tags for configuration text
Use MantisBT, fix grammar and stop yelling
Localisation updates from https://translatewiki.net.
Localisation updates from https://translatewiki.net.
Update supported languages

Also remove an inline tab I spotted.
bug_report.php: fix warning when not using attachments

When attachments are not used, 'ufile' is not defined, so $t_files
becomes NULL (line 150) causing the 'Invalid argument supplied for
foreach' warning.

Fixes #17322
Fix #17324: remove var_dump()
Issue #17322: apply same logic in bug_file_add.php
Provide a description for unknown error types
Separate error type from description with colon

This makes the error message look more like standard PHP errors.
Exit with an error code of 1

This allows the calling script to respond in an appropriate manner in
case an error occurs.
Only exit if error type is configured to HALT

Makes CLI script behave like the web app
Only print message if error type is configured to do so

If display method == DISPLAY_ERROR_NONE, don't print anything.
Don't fall through web-specific error handling

If a non-critical error occurs and we continue code execution as
configured in $g_display_errors, the web-specific handling should not be
executed.
Print backtrace when show_detailed_errors == ON