OpenWrt DSA Mini-Tutorial

[Rich Brown]

I have updated the DSA Mini-tutorial in the playground: https://openwrt.org/playground/richb/dsa-mini-tutorial

I finished the first section ("Bridging all LAN ports"), and I am going to stop editing now, because:

1) I need someone else to look at the overall format of the document
2) I made some bold assertions and simplifications of the language in the document. But because I don't really understand DSA, I may be totally wrong...
3) If it's not right, we won't have to patch up the remainder, that is substantially unchanged from the Forum post.

Please check it out and either change it, or let me know what needs to be fixed. Thanks.

Rich