Add set to TemplateInstance

[merlinstardust]

I would have preferred to use the get method already set up but that only would have worked with the reactive-var package. This works regardless of if you have it.

[mitar]

Ha? Here are some assumptions that any field on the template instance when you have reactive var package is a reactive var? This is a bit hard assumption. You should do some instanceof check.

[merlinstardust]

You mean instead of doing if (Package['reactive-var']), I should do if (previousValue instanceof ReactiveVar)?

[mitar]

if (Package['reactive-var'] && previousValue instanceof Package['reactive-var'].ReactiveVar) or something like that.

[merlinstardust]

Added