Issue 0012253: Implement management page to view workflow graph

Bernard de Rubinat contributed a patch to implement a workflow graph
using the existing GraphViz API for rendering. This patch will add a new
page the Manage => Configuration menu to show a graph of the workflow
(status transitions) for the currently selected project.

The proposed functionality was cleaned up and extended in the following
ways:

1) Added workflow_api for functions that are used for working with
workflows. This API is already used by two MantisBT pages.

2) Place the workflow graph on a separate page in the management
console. There wasn't enough space within the
manage_config_workflow_page.php page.

3) Use the 'dot' tool for generating the graph rather than 'neato'. This
new format is more suitable for displaying workflows.

4) Refactored the code used to print the manage configuration menu. This
newer format would be better used as a generic print_menu(...) function
in the future (serving multiple different menus).

Contributed-by: Bernard de Rubinat bernard.derubinat@gmail.com
Contributed-by: David Hicks hickseydr@optusnet.com.au