#19 Auto-complete for well-formedness

[Brion Swanson]

A nice feature to add would be to allow auto-complete
for XML documents that do not have an associated
grammar, but merely auto-completion with tag name matching.

Example:

<!-- cursor stays after > auto-complete adds closing
tag '*' surrounds auto-completed tag, '|' represents
the cursor position after typing '<my_tag>' -->

<my_tag>|*</my_tag>*

Alternately, a hot-key (combination) could be used to
invoke autocompletion such as CTRL-SPACE as in the Java
Perspective for method-completion. Eventually, this
hot-key combination may be user-defined as in the Java
Perspective.