Enh 0001649: Replace 'Assign to Me' with 'Assign To:' and dropdown of developers.

M bug_assign.php

• Support assigning a bug to a user other than the currently logged in user.

M core/access_api.php

• Added the possibility to check access for a user other than the current logged in user.

M core/bug_api.php

• Added checking that the user we are assign the bug to, has the appropriate access level.

M core/constant_inc.php

• Added a constant for new error message.

M core/html_api.php

• (html_button_bug_assign): removed
• (html_button_bug_assign_reporter): removed
• (html_button_bug_assign_to): added

M lang/strings_english.txt

• Removed some strings and added a couple.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2340 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9