url-shortener: implements rfd 4 (#65)

* DB Done. Adding new entry in db request Done

* add short url render and redirection

* separate functionality update

* removed global var db

* added two fields in List: owned_id and active?

* fixed minor issues

* db changes

* added NameAlreadyTaken error

* moved address check outside of Create

* changed several minor issues

* chenged opendb func with newsqlitestore
diff --git a/apps/url-shortener/.gitignore b/apps/url-shortener/.gitignore
new file mode 100644
index 0000000..4042c7b
--- /dev/null
+++ b/apps/url-shortener/.gitignore
@@ -0,0 +1,2 @@
+# Exclude SQLite database file
+*.db