admin_manual/source_installation: Fixes in PHP prerequisites and Apac…

…he configuration

* PHP: Both PostgreSQL (nextcloud/server#367) and SQLite (nextcloud/server#481)
  are handled by PDO in recent Nextcloud versions
* Apache: Distributed configuration files (".htaccess") need to be readable
  only

admin_manual/installation/source_installation.rst

@@ -56,9 +56,9 @@ Required:
 
 Database connectors (pick the one for your database:)
 
-* PHP module sqlite (>= 3, usually not recommended for performance reasons)
+* PHP module pdo_sqlite (>= 3, usually not recommended for performance reasons)
 * PHP module pdo_mysql (MySQL/MariaDB)
-* PHP module pgsql (requires PostgreSQL >= 9.0)
+* PHP module pdo_pgsql (requires PostgreSQL >= 9.0)
 
 *Recommended* packages:
 
@@ -270,7 +270,7 @@ Additional Apache Configurations
 Pretty URLs
 -----------
 
-Pretty URLs are created automatically when ``.htaccess`` is writable by the 
+Pretty URLs are created automatically when ``.htaccess`` is readable by the 
 HTTP user, ``mod_env`` and ``mod_rewrite`` are installed, and 
 ``'overwrite.cli.url'`` in your ``config.php`` is set to any non-null value.