Packages: added logrotate configuration for Debian packages.

While here, made logrotate configuration consistent between rpm and deb.

This closes #323 issue on GitHub.

pkg/deb/debian/unit.logrotate

@@ -0,0 +1,15 @@
+/var/log/unit.log {
+    daily
+    missingok
+    rotate 7
+    compress
+    delaycompress
+    nocreate
+    notifempty
+    su root root
+    postrotate
+        if [ -f /var/run/unit.pid ]; then
+            /bin/kill -SIGUSR1 `cat /var/run/unit.pid`
+        fi
+    endscript
+}