Cleanup file upload handling some more.

I added some new config options to allow you to set thresholds for project file uploading and bug file uploading.

I added a config option to control whether reporters can always add files to their own bugs.

I added two new file_api functions that can be called to check whether a user can upload a file. It takes into account access thresholds, whether file uploading is enabled, etc. These functions should be used everywhere in the code... if they're inadequate we can improve them.

• bug_file_add.php: use new file_api functions for file upload access check
• bug_file_upload_inc.php: check if we can upload (using new file_api functions) and return if not (don't error, that's not very useful)
• bug_report.php: use new file_api functions for file upload access check
• bug_report_advanced_page.php: use new file_api functions for file upload access check
• bug_report_page.php: use new file_api functions for file upload access check
• bug_view_advanced_page.php: use new file_api functions and seperate checks for viewing attachments from checks for uploading new ones
• bug_view_page.php: use new file_api functions and seperate checks for viewing attachments from checks for uploading new ones
• config_defaults_inc.php
  (g_upload_project_file_threshold): new option controlling the access level needed to upload project files
  (g_upload_bug_file_threshold): new option controlling the access level needed to upload files attached to a bug
  (g_allow_reporter_upload): new option that allows reporters to upload files to their reported bugs even if their access level is lower than that specified by the above option
• proj_doc_add.php: use new file_api functions for file upload access check
• proj_doc_add_page.php: use new file_api functions for file upload access check
• core/file_api.php
  (file_allow_project_upload): new function that determines whether a user can upload a file to thegiven project
  (file_allow_bug_upload): new function that determines whether a user can upload a file to the given bug (or to a new bug in the current project)
• core/html_api.php
  (print_doc_menu): use new file_api functions to determined whether to display the "Add File" link
• doc/ChangeLog: add comments about new config options

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1668 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9