Possibility to allow external selection of plantuml.jar

[timur-han]

Hi,

Thank you for the contribution.

Is it possible to configure plantuml.jar to be used to render the files? Plantuml has sometimes backward compatiblity issues and in such cases, I think it will help us to select the right version.

[kferrone]

I am getting a similar issue with too new of a graphviz dot installation. If only I could select my own plantuml jar.

[hallvard]

This is too error prone and would require some classpath magic that's difficult to do right in an OSGi context.