Hello,

Markup structures like "#+begin_src" and "#+being_quote" can be
inserted using the command `org-insert-structure-template'.  In much
of the documentation, these structures are called "blocks", including
the existing documentation for `org-insert-structure-template'.
I personally found the name `org-insert-structure-template' harder to 
remember when wanting to insert a "block", because I kept assuming that 
the word "block" would be used in the name of the command.

This attached patch adds the alias `org-insert-block-template' for 
`org-insert-structure-template', which I would have found more memorable 
when learning how to use Org's markup blocks.

Thank you.