node: Move NPM into a separated pacakge

In order to reduce flash requirements and also to disallow running NPM on the target
move NPM out of the default NodeJS package.
In order to allow adding NPM via opkg install, move it to a separated
directory

Signed-off-by: Ygal Blum <ygal.blum@gmail.com>

lang/node-serialport/Makefile

@@ -10,7 +10,7 @@ include $(TOPDIR)/rules.mk
 PKG_NPM_NAME:=serialport
 PKG_NAME:=node-$(PKG_NPM_NAME)
 PKG_VERSION:=3.0.0
-PKG_RELEASE:=3
+PKG_RELEASE:=4
 
 PKG_SOURCE:=$(PKG_NPM_NAME)-$(PKG_VERSION).tgz
 PKG_SOURCE_URL:=http://registry.npmjs.org/$(PKG_NPM_NAME)/-/
@@ -26,7 +26,7 @@ PKG_LICENSE_FILES:=LICENSE
 include $(INCLUDE_DIR)/package.mk
 
 define Package/node-serialport
-  DEPENDS:=+node
+  DEPENDS:=+node +node-npm
   SUBMENU:=Node.js
   SECTION:=lang
   CATEGORY:=Languages