Tree format needs a blank space after the bullet

[alex-mashin]

Tree format needs a blank space after the bullet. Expected:

* node1
** node11

Actual:

*node1
**node11

Reason: after this change, {{#ask:...|format=tree}} can be safely wrapped with

{{#tag:plantuml|
@startmindmap
{{#ask:...|format=tree}}
@endmindmap
}}

as is.

if External Data or some other extension provides the tag <plantuml>.

Now the output of {{#ask:...|format=tree}} has to be processed with a regular expression to inject the needed spaces. Exampe.