Some modifications

[CuloArdido]

I've been making adjustments to solve some of the points mentioned in #1.

Now the quoted strings are optional when passing parameters to the procedures, in that way, strings can be used as identifiers, making them differentiate easily from normal strings (resolve point 1 in #1).

Another change that I made was to customize the style and orientation of the arrows in the pair(), doublepair() and child() procedures with extra parameters (solves point 5 in #1), which is quite useful to have a more detailed control in that aspect, and may also solve that problem with the parental bond between parent/child. I imagine that with rectangles you can do the same using skinparam or the <style> tag but I haven't checked.

Finally I also updated example.puml making the identifiers less ambiguous (solving point 2 in #1) and add some examples of custom arrows. This is how the diagram looks like with these changes:

[dgutson]

Thanks @CuloArdido , great patch and great alias!! :)