Fix .html to .md

content/pages/en/presentation/stand.html

content/pages/en/presentation/stand.md

content/pages/en/presentation/stand.md.save

content/pages/en/presentation/talks.html

content/pages/en/presentation/talks.md

content/pages/en/solutions/cloud.html

content/pages/en/solutions/cloud.md

content/pages/en/solutions/network.html

content/pages/en/solutions/network.md

content/pages/en/solutions/sis.html

content/pages/en/solutions/sis.md

content/pages/en/support/community.html

content/pages/en/support/community.md

content/pages/en/support/professional.html

content/pages/en/support/professional.md