"usherConfigured" to denote whether we render links to the usher
control functions in the forge administration
* src/IDF/Scm/Monotone.php: moved IDF_Scm_Monotone_Stdio into
separate file src/IDF/Scm/Monotone/Stdio.php
* src/IDF/Scm/Usher.php: new class to query and modify the state
of a running usher instance
* src/IDF/Views/Admin.php: add actions to query the list of
configured servers, edit their status, view their open connections
and control the state of the usher as a whole
* src/IDF/conf/idf.php-dist: optional usher configuration added;
mail address of monotone-users added; spelling changes
* src/IDF/conf/urls.php: added needed URLs for usher actions
* src/IDF/templates/idf/gadmin/base.html: usher links
