Configurable HTML output with documentation sets

[dirc]

We use html output a lot, great for visibility within the project.

• Rather than do the whole model every time, (which is time consuming with a large model, even if I have only made one change!), I only output certain packages, but I have to configure them every time.
  
• Futher to this, I have a lot of framework classes imported into my model, and I don't want to generated these every time, since they do not change.

I would like to be able to create and configure html documentation sets as follows: (Probably also applicable to RTF doc)

• Have the ability to output each package to a configured location.
  
• Within a documentation set, have the ability to enable/disable the generation of each package.
  
• For each package, have the ability to only re-generate the documentation if there have been changes since that last time it was output.
  
• Finally, for each documentation set, have the option to regenerate completely.