#53 Add 'append' and 'insert' to Variable

[Jason Heddings]

I use <var> many times to build argument strings for an <exec> call, especially since <exec> doesn't allow <if> or conditional <arg> elements. It would be great if <var> could just have 'append' and 'insert' methods to make this a little cleaner of a process. I've attached a patch that I think accomplishes these things.

Also, if <var> could be made conditional, that would be even better.

[Jason Heddings]