[typo] Keeping Typo's codebase separate from site-specific customisations

[Tim Lucas]

Just thought Duane's recent post might have some relevance to Typo:
http://thread.gmane.org/gmane.comp.lang.ruby.rails/14513

Might be a good way to keep Typo core separate from from site-specific 
customisations... though it would quickly become unmaintainable if 
people are overriding things willy-nilly. Nothing can replace a set of 
well thought-out and documented extension points.

- tim lucas