Installer: Refactor and give each searver its own directory

Change-Id: I1db2929e7a35b6f92022dec0c6506d68e0297563
diff --git a/core/installer/server/form.go b/core/installer/server/form.go
new file mode 100644
index 0000000..05bbc44
--- /dev/null
+++ b/core/installer/server/form.go
@@ -0,0 +1,14 @@
+package server
+
+import (
+	"fmt"
+	"net/url"
+)
+
+func GetFormValue(v url.Values, name string) (string, error) {
+	items, ok := v[name]
+	if !ok || len(items) != 1 {
+		return "", fmt.Errorf("%s not found", name)
+	}
+	return items[0], nil
+}