Change greek characters

[nikkos]

I am greek and I think for slugs it is better to not use numbers.(not nice)
I changed two letters:
"Θ" was "8"
"θ" was "8"
"Ξ" was "3"
"ξ' was "3"
and change them to:
"Θ" to "TH"
"θ" to "th"
"Ξ" to "KS"
"ξ' to "ks"

I hope I helped.

[h4cc]

Thanks for this!
I mostly collected these replacements from other projects hoping they are correct ;)