Do not redirect after creating the first project

When the first project is created after installing MantisBT, an
application error 2800 occurs when submitting the changes from
manage_proj_create_page.php, although the project is created
successfully.

Regression introduced by b1a1bbaeb690b7611899ae8075586d655155d18c

Fixes #16337
Translate custom field names

Custom fields are displayed with their name, disregarding their
localization :
- in the history log
- in the custom fields section, in the project management page

Thanks to jmonin for the patch.

Fixes #12470

Conflicts:
	manage_proj_edit_page.php
Remove useless code
When sorting by due_date, display undefined values last

Markus' original patch was modified to simplify the code and reduce
duplication, fix a couple typos in comment text and reword the
commit message.

Fixes #16259
Remove DISTINCT clause from filter_get_bug_rows query

Fixes #16259 PostgreSQL error when filtering by due_date ASC
Follow-up fix for custom field names translations

In the case where we have multiple custom strings localized to the same
string, commit c174d88fc4f6a92e5bff0f7660688f1757c4cdaf would make it
impossible to distinguish them.

While this should not be a major issue in the bug history (as it doesn't
make sense to have more than one fields with a given localized name
within a given project), it is important that in custom field management
as well as project management pages custom fields are uniquely
identified with their "system" name to ensure there is no confusion.

This commit adds a new API function custom_field_get_display_name() that
will append the localized name to the field name, and which is called
from the above-mentioned pages.

Issue #12470

Conflicts:
	manage_proj_edit_page.php
Added new logo image without "mantis bug tracker" text

Square cropped copy of original mantis_logo.png
Merge branch 'master' into 13x