refacto: move some code into actions

(non breaking, old assignments link to new assignments)
- move lib.collapse-all into actions/collapse-all
- move lib.dir-up into actions/dir-up
- move lib.change-dir into actions/change-dir
- use setup option for change-dir global (and use the old option for
  setup)

README.md

@@ -96,6 +96,11 @@ require'nvim-tree'.setup {
   trash = {
     cmd = "trash",
     require_confirm = true
+  },
+  actions = {
+    change_dir = {
+      global = false,
+    }
   }
 }
 ```
@@ -110,7 +115,6 @@ let g:nvim_tree_highlight_opened_files = 1 "0 by default, will enable folder and
 let g:nvim_tree_root_folder_modifier = ':~' "This is the default. See :help filename-modifiers for more options
 let g:nvim_tree_add_trailing = 1 "0 by default, append a trailing slash to folder names
 let g:nvim_tree_group_empty = 1 " 0 by default, compact folders that only contain a single folder into one node in the file tree
-let g:nvim_tree_change_dir_global = 1 "0 by default, use :cd when changing directories.
 let g:nvim_tree_disable_window_picker = 1 "0 by default, will disable the window picker.
 let g:nvim_tree_icon_padding = ' ' "one space by default, used for rendering the space between the icon and the filename. Use with caution, it could break rendering if you set an empty string depending on your font.
 let g:nvim_tree_symlink_arrow = ' >> ' " defaults to ' ➛ '. used as a separator between symlinks' source and target.