减号、星号和井号后跟一个或多个制表符，也是表示列表条目
Add function vimwikifile2markdownfile(wikif,mkdf,mkdtype)
Remove some unusefull comments and functions
Keep blank lines before blockquotes
Remove g:did_vimwiki2markdown_loaded
Add two user command: VimwikiAll2MkdFile and VimwikiBufs2MkdFile