doc, vtysh: Fixup of history handling

This fix does two things:

1) If the ${HOME}/.history_quagga file does not exist, create it
for history storing.
2) Allow vtysh -c "..." commands to be stored in history file
as well

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/doc/vtysh.1 b/doc/vtysh.1
index de4913e..a2afa9f 100644
--- a/doc/vtysh.1
+++ b/doc/vtysh.1
@@ -76,6 +76,9 @@
 .BI /usr/local/etc/Quagga.conf
 The default location of the integrated Quagga routing engine config file
 if integrated config file is in use (not default).
+.TP
+.BI ${HOME}/.history_quagga
+Location of history of commands entered via cli
 .SH WARNING
 This man page is intended to be a quick reference for command line
 options. The definitive document is the Info file \fBQuagga\fR.