Align nginx configuration to production for webserver-alkane

Summary:
There was a drift between production and rOPS in Ysul for webserver-legacy sites.
This change ensures we're sync between repository and production for webserver-alkane.

Mainly:

• fastcgi_params is now includes/fastcgi on several PHP sites
• dereckson.be WordPress configuration uses experimentally WordPress SaaS config
• Dotclear to WordPress migration fixes
• Let's Encrypt location blocks should also be present in TLS server blocks
• alias www.nasqueron.org/software

Ref T1803.
Ref T1828.

Test Plan:
nginx -t

no-op as those changes reflect current production state

Reviewers: dereckson, ledesillusionniste

Reviewed By: dereckson

Maniphest Tasks: T1828, T1803

Differential Revision: https://devcentral.nasqueron.org/D3190