Update the whole documentation

Hello,

Sorry I'm opening another WIP but I have some questions. I hope this time I will be a little be faster to update the code. Here's the roadmap:

* [x] **Update the deprecated commands** : According to the `UPDATE.md`, the commands use in the documentation have all been updated (except those which haven't been yet refactored). Also change all occurence of propel-gen with the propel script.

* [ ] **Update all commands' output**

* **Update deprecated methods and objects** :
    * [x] `getConnection` -> `getReadConnection` / `getWriteConnection`
    * [x] `Persistent` -> `ActiveRecordInterface`
    * [ ] `BaseObject`
    * [x] `containsColumn` -> `hasColumn`
    * [x] `addParameter(array)` -> `setParameter(name, value)`

* [ ] **Remove code related to PHP < 5.4** : Remove all mentions to options/code related to PHP 5.2 ou 5.3 (e.g. magic_quotes).

* [ ] **Write a guide to upgrade from Propel 1.x to 2.0** : Write a guide widely based on the `UPDATE.md` file and with the new stuff (e.g. new folder's structure).

* [ ] **Update all relative paths that point to Propel's installation directory**

My first question is about `BaseObject`. Is it enough to change any `extends` statement from this object to a `implements` one of `ActiveRecordInterface`? At this level, I think that the update file should be improved.

My other question is about some `propel-gen` commands which doesn't seem to be present. These commands are:
  * dbd2propel
  * datasql
  * datadump

I haven't found anything about them (searching on the issue tracker and with `git log --grep`).

Have a nice day