cleanup documentation

Remove level 3 (page title) from TOC and add permalinks.
Also fix and update some minor stuff in the docs.

docs/admin/Installation.md

@@ -1,3 +1,5 @@
+# Basic Installation
+
 This page contains generic installation instructions for Nominatim and its
 prerequisites. There are also step-by-step instructions available for
 the following operating systems:
@@ -15,9 +17,9 @@ and can't offer support.
   * [Docker on Kubernetes](https://github.com/peter-evans/nominatim-k8s)
   * [Ansible](https://github.com/synthesio/infra-ansible-nominatim)
 
-# Prerequisites
+## Prerequisites
 
-## Software
+### Software
 
 For compiling:
 
@@ -49,22 +51,22 @@ For running continuous updates:
 
   * [pyosmium](http://osmcode.org/pyosmium/)
 
-## Hardware
+### Hardware
 
 A minimum of 2GB of RAM is required or installation will fail. For a full
 planet import 32GB of RAM or more strongly are recommended.
 
-For a full planet install you will need about 600GB of hard disk space (as of
-January 2017, take into account that the OSM database is growing fast). SSD disks
+For a full planet install you will need at least 700GB of hard disk space
+(take into account that the OSM database is growing fast). SSD disks
 will help considerably to speed up import and queries.
 
 On a 6-core machine with 32GB RAM and SSDs the import of a full planet takes
 a bit more than 2 days. Without SSDs 7-8 days are more realistic.
 
 
-# Setup of the server
+## Setup of the server
 
-## PostgreSQL tuning
+### PostgreSQL tuning
 
 You might want to tune your PostgreSQL installation so that the later steps
 make best use of your hardware. You should tune the following parameters in
@@ -91,13 +93,13 @@ Don't forget to reenable them after the initial import or you risk database
 corruption. Autovacuum must not be switched off because it ensures that the
 tables are frequently analysed.
 
-## Webserver setup
+### Webserver setup
 
 The `website/` directory in the build directory contains the configured
 website. Include the directory into your webbrowser to serve php files
 from there.
 
-### Configure for use with Apache
+#### Configure for use with Apache
 
 Make sure your Apache configuration contains the required permissions for the
 directory and create an alias:
@@ -116,7 +118,7 @@ build directory.
 After making changes in the apache config you need to restart apache.
 The website should now be available on http://localhost/nominatim.
 
-### Configure for use with Nginx
+#### Configure for use with Nginx
 
 Use php-fpm as a deamon for serving PHP cgi. Install php-fpm together with nginx.