split packages into core and extra

both are used to clean up, so none are removed, but only core is sync'd
explicitly, so extra packages are not installed

.emacs

@@ -48,7 +48,7 @@
 
 (add-to-list 'el-get-recipe-path "~/.emacs.d/el-get-user/recipies")
 (setq el-get-user-package-directory "~/.emacs.d/el-get-user/init-files")
-(setq my-packages
+(setq my-packages-core
       '(el-get
         smart-mode-line
         avy
@@ -60,8 +60,9 @@
         magit
         undo-tree
         hydra
-        multiple-cursors
-        lua-mode
+        multiple-cursors))
+(setq my-packages-extra
+      '(lua-mode
         pkgbuild-mode
         arduino-mode
         gnuplot-mode
@@ -74,8 +75,9 @@
         jedi-core
         company-jedi))
         ;;auctex))
-(el-get-cleanup my-packages)
-(el-get 'sync my-packages)
+(el-get-cleanup (append my-packages-core my-packages-extra))
+(el-get 'sync my-packages-core)
+(el-get 'sync)
 
 ;;allow saving files that need root
 (defun find-file-as-root(buffer)