Add directorySelector

As discussed at phone meeting the filter is not allowed.
Other design issues are discussed in modelica#3187
Closes modelica#3187

chapters/annotations.tex

@@ -1289,6 +1289,7 @@ \section{Graphical User Interface}\label{annotations-for-the-graphical-user-inte
   Boolean colorSelector = false;
   Selector loadSelector;
   Selector saveSelector;
+  Selector directorySelector;
   String groupImage = "";
   Boolean connectorSizing = false;
 end Dialog;
@@ -1306,7 +1307,7 @@ \section{Graphical User Interface}\label{annotations-for-the-graphical-user-inte
 An empty \lstinline!group! (the default) means tool-specific choice of group.
 The order of components (and class definitions) within each group and the order of the groups and tabs are according to the declaration order, where inherited elements are added at the place of the extends.
 
-A component shall have at most one of \lstinline!showStartAttribute=true!, \lstinline!colorSelector=true!, \lstinline!loadSelector!, \lstinline!saveSelector! or \lstinline!connectorSizing=true!.
+A component shall have at most one of \lstinline!showStartAttribute=true!, \lstinline!colorSelector=true!, \lstinline!loadSelector!, \lstinline!saveSelector!, \lstinline!directorySelector!, or \lstinline!connectorSizing=true!.
 
 \begin{example}
 When \lstinline!group! is empty, a tool may place parameters in the group ``Parameters'', and place variables with \lstinline!showStartAttribute = true! in the group ``Start Attributes''.
@@ -1328,6 +1329,10 @@ \section{Graphical User Interface}\label{annotations-for-the-graphical-user-inte
 \lstinline!caption! is a caption for display in the file dialog.
 \lstinline!loadSelector! is used to select an existing file for reading, whereas \lstinline!saveSelector! is used to define a file for writing.
 
+The presence of \lstinline!directorySelector! specifying \fmtannotationindex{Selector} suggests the use of a file dialog to select an existing directory. 
+The \lstinline!filter! may not be used.
+The \lstinline!caption! is a caption for display in the file dialog.
+
 The \lstinline!groupImage! references an image using an URI (see \cref{external-resources}), and the image is intended to be shown together with the entire group (only one image per group is supported).
 Disabling the input field will not disable the image.
 The background of the \lstinline!groupImage! and any image used in HTML-documentation is recommended to be transparent (intended to be a light color) or white.