Patch to add theme support

Please find attached the patch of my rewrites to views_plugin_style_lineage_nested.inc with the following changes:

1. Added theme support. I've changed nested_list() so that it calls the Views theme in its recursion. Instead of going straight to output, the return from nested_list() copies over the existing array element (so Array objects are replaced with themed output strings).
2. As a result, I made rudimentary customisations to the default Views list template and attached it as views-view-lineage-nested.tpl_.txt. You'll obviously have to change _.txt in the file name to .php, but you can now copy and theme this in your own site theme.
3. I moved the row rendering from render() to render_nesting(). This is to reduce the number of times which the taxonomy has to be looped through by 1.
4. Because themes automagically handle headers, header() is obsolete (and removed).
5. I changed variable names in render(), nested_list() and render_nesting() to make them more consistent with Views terminology. I hope this doesn't offend anybody.
6. I figured out how to run render_nesting() so that it wouldn't have to call eval(). You're welcome.
7. Miscellaneous changes I can't remember. Check the diff (also attached)

Note the comment around line 210: @todo: remove this line once issue #1201054: Extra \n in term_lineage.lineage is resolved. This is to compensate for how the module stores information. This line of code will break the rendering once #1201054: Extra \n in term_lineage.lineage is fixed!!!