Add support for endnote syntax

[borgar]

Support should be added for endnote syntax. Textile-lang.com gives the following example:

The sun is reportedly hot,[#hot] just like freshly baked potatoes.[#hot] Ice is cold.[#cold]

note#hot. Ouch.

note#cold. Brrr.

notelist:1.

Endnote syntax consists of three separate elements:

• [x] Support inline note reference: [#LABEL] | [#LABEL!]
• [x] Support block note definition: note#LABEL. TEXT | note#LABEL^. TEXT
• [x] Support block note list: notelist. | notelist:A^+.