some more FAQ additions
Merge pull request #1968 from pieterlexis/port-faq

some more FAQ additions
Add disable-dnssec to pdnssec docs (closes #641)
initial start of porting manpages to markdown
migrate more manpages
WIP zone2ldap.8
Finish zone2ldap.8.md
Show mandatory options in synopsis
Add manpage for zone2sql
Update manpage for pdnssec.8
Add the options to dnsscope manpage
Make manpages consistent with eachother
Build the manpages

  * Build into pdns/docs/manpages-built
  * gitignore pdns/docs/manpages-built
  * Remove building of 'old' manpages
Remove old manpages
Remove old manpages from gitignore
Build manpages into pdns/docs

This doesn't require any changes to the upper-level manpages (backwards
compatibility FTW!)
Let make handle building the manpages
Update set-nsec3 in pdnssec.8.md
Fix glaring oversight
Remove unneeded escaping of underscores