full paths for .gitignore + ignore .DS_Store files

Without this then we can not add files to "sbin" directory
under nanobsd/Files/usr/local/sbin.

Add .DS_Store for mac people.

.gitignore

@@ -2,10 +2,11 @@
 *.swp
 *.mo
 *.o
-docs/api/_build/
-gui/local_settings.py
-FreeBSD/
-filtered-patches/
-os-base/
-pbi/
-sbin/
+.DS_Store
+/docs/api/_build/
+/gui/local_settings.py
+/FreeBSD/
+/filtered-patches/
+/os-base/
+/pbi/
+/sbin/