Editors: Automatically add editor/document id to context and use that

instead of manually adding a context everywhere.

Change-Id: I4336015a6d19349171a255e949da89b0013d6700
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/genericprojectmanager/genericprojectconstants.h

@@ -37,7 +37,6 @@ const char PROJECTCONTEXT[]     = "GenericProject.ProjectContext";
 const char GENERICMIMETYPE[]    = "text/x-generic-project"; // ### FIXME
 
 // Contexts
-const char C_FILESEDITOR[]      = ".files Editor";
 const char FILES_EDITOR_ID[]    = "QT4.FilesEditor";
 
 const char FILES_MIMETYPE[]     = "application/vnd.qtcreator.generic.files";