Adding table of content tag to documentation

docs/simplesamlphp-advancedfeatures.txt

docs/simplesamlphp-authproc.txt

docs/simplesamlphp-automated_metadata.txt

docs/simplesamlphp-changelog.txt

docs/simplesamlphp-errorhandling.txt

docs/simplesamlphp-features.txt

docs/simplesamlphp-googleapps.txt

docs/simplesamlphp-idp-more.txt

docs/simplesamlphp-idp.txt

docs/simplesamlphp-install.txt

docs/simplesamlphp-maintenance.txt

docs/simplesamlphp-modules.txt

docs/simplesamlphp-reference-idp-hosted.txt

docs/simplesamlphp-reference-idp-remote.txt

docs/simplesamlphp-reference-sp-hosted.txt

docs/simplesamlphp-reference-sp-remote.txt

docs/simplesamlphp-sp-api.txt

docs/simplesamlphp-sp-migration.txt

docs/simplesamlphp-sp.txt

docs/simplesamlphp-theming.txt