Implement Amazon Cloud Drive - fixes #45

* Optional interfaces Copier, Mover, DirMover not done

docs/content/overview.md

@@ -0,0 +1,71 @@
+---
+title: "Overview of cloud storage systems"
+description: "Overview of cloud storage systems"
+type: page
+date: "2015-09-06"
+---
+
+# Overview of cloud storage systems #
+
+Each cloud storage system is slighly different.  Rclone attempts to
+provide a unified interface to them, but some underlying differences
+show through.
+
+## Features ##
+
+Here is an overview of the major features of each cloud storage system.
+
+| Name                   | MD5SUM  | ModTime | Case Sensitive | Duplicate Files |
+| ---------------------- |:-------:|:-------:|:--------------:|:---------------:|
+| Google Drive           | Yes     | Yes     | No             | Yes             |
+| Amazon S3              | Yes     | Yes     | No             | No              |
+| Openstack Swift        | Yes     | Yes     | No             | No              |
+| Dropbox                | No      | No      | Yes            | No              |
+| Google Cloud Storage   | Yes     | Yes     | No             | No              |
+| Amazon Cloud Drive     | Yes     | No      | Yes            | No              |
+| The local filesystem   | Yes     | Yes     | Depends        | No              |
+
+### MD5SUM ###
+
+The cloud storage system supports MD5SUMs of the objects.  This
+is used if available when transferring data as an integrity check and
+can be specifically used with the `--checksum` flag in syncs and in
+the `check` command.
+
+### ModTime ###
+
+The cloud storage system supports setting modification times on
+objects.  If it does then this enables a using the modification times
+as part of the sync.  If not then only the size will be checked by
+default, though the MD5SUM can be checked with the `--checksum` flag.
+
+All cloud storage systems support some kind of date on the object and
+these will be set when transferring from the cloud storage system.
+
+### Case Sensitive ###
+
+If a cloud storage systems is case sensitive then it is possible to
+have two files which differ only in case, eg `file.txt` and
+`FILE.txt`.  If a cloud storage system is case insensitive then that
+isn't possible.
+
+This can cause problems when syncing between a case insensitive
+system and a case sensitive system.  The symptom of this is that no
+matter how many times you run the sync it never completes fully.
+
+The local filesystem may or may not be case sensitive depending on OS.
+
+  * Windows - usuall case insensitive
+  * OSX - usually case insensitive, though it is possible to format case sensitive
+  * Linux - usually case sensitive, but there are case insensitive file systems (eg FAT formatted USB keys)
+
+Most of the time this doesn't cause any problems as people tend to
+avoid files whose name differs only by case even on case sensitive
+systems.
+
+### Duplicate files ###
+
+If a cloud storage system allows duplicate files then it can have two
+objects with the same name.
+
+This confuses rclone greatly when syncing.