Use string formatting for XML output

[ghost]

Currently the BCE uses raw string output to create XML elements:

self.writel(S_FX, 3, '<newparam sid="' + surface_sid + '">')

This is both hard to read and hard to write. The Blender team suggests using string formatting like they did here:

fw('%s<Coordinate USE=%s />\n' % (indent, mesh_id_coords))

I suggest something entirely different and in my opinion easier to both read and write (since it takes care of indentation automatically, and is also less error-prone) - using xml.etree.cElementTree to generate the XML (which is fast enough) and then use xml.dom.minidom to prettify/indent it (both are included in the standard library).

[set-killer]

This is related to about 30-40% of the code.

Which of the both methods is better to use? In my opinion using xml.etree.cElementTree would not make the code more easy to read and it will be harder to make the parenting of the XML nodes.
Anyone with experience on this?

(Just discussing the issue...)

[ghost]

@set-killer I think that if unit tests for the XML generation are written, the format method can be just as reliable (and faster).

[ghost]

I think it's best if at least for the time being, since it's what the Blender dev requested and it'd be great to have Blender devs working on this plugin as soon as possible, we go ahead with format for the XML output.

@set-killer If you can take this and push a commit in a reasonable time please tell me, otherwise I can do it myself in a few days (hopefully).

[set-killer]

Yes, working on it.