Add related terms & synonym editing

Looks useful, thanks.

Please:

1. run this through the coder module to clean up code style issues.
2. clean up a few white-space and indentation issues.
3. fix variable names $node_arr -> $node_array.
4. capitalise comments and terminate with a period.
5. remove the warning. I will very likely be enabling an optional two-way control between nodes and terms. Perhaps this can be a configuration option. Alternatively, it would be ideal if we can implement proper access control to these vocabularies.
6. check hook_nodeapi: the related terms and synonyms don't seem to get passed successfully during node creation. Works fine during node updates.
7. try to avoid the array casts in hook_nodeapi as they look unnecessary and very expensive. You could perhaps replace it with $a->$b, where $b is a string.
8. bunch the two form variables together using a #tree => TRUE.

Thanks mate.
-K

Forgot to change the status :)