Update requirements class url

[ebocher]

The requirements class url refers to http://www.opengis.net/spec/symbology-1/2.0/req/core

We must update it to the new chapter name.

What about :

http://www.opengis.net/spec/cartosym-1/2.0/req/core

[maxcollombin]

also applies to the following items

[maxcollombin]

... and also to parts 2, 3 & 4 (although we'll look at these later)

Note

change the reference to CartoSym 2.0 (not 1.0)

[ebocher]

Waiting @jerstlouis push to fix this issue

[maxcollombin]

Waiting @jerstlouis push to fix this issue

We also need to update parts 2,3,4 (see comment above)