Password reset functionality

On the `reset` page an email address can be submitted. If an account
associated with the submitted email address an email is sent
containing an URL. This URL can be used to set a new password.

- Add GPLv3 for licensing
- Add dependencies
  - `rocket_contrib` to be able to use handlebar templates
  - `anyhow` to handle errors
  - `log` for logging
  - `ldap3` to communicate with a LDAP server
  - `lettre` and `lettre_email` to handle the generation of emails and
    to send them
  - `rand` to generate random keys
- Add `README.org` which is also used to generate `README.md`
- Add configuration parameters
  - domain
  - LDAP
    - server
    - base
    - filter
    - bind
    - password
- Change default development address to 0.0.0.0
- Add structs to handle data
- Add functions to handle password reset actions
  - `reset_prepare()` to generate a new key, send it to the requestor
    and keep it in the memory
  - `set_password()` to check for the key and set the password
- Add routes
- Add tests
- Add templates
  - `reset.html.hbs` to submit an email address
  - `reset_key.html.hbs` to set the new password

README.md

@@ -0,0 +1,87 @@
+
+# Table of Contents
+
+1.  [ldap0r](#org5453f05)
+    1.  [Installation](#org225ba27)
+    2.  [Todo List](#org54f2856)
+        1.  [Password reset <code>[5/10]</code>](#org09786dd)
+        2.  [Configuration <code>[0/5]</code>](#orgb93c7a2)
+        3.  [Login Section (not sure if going to happen)](#orga66a23f)
+
+
+<a id="org5453f05"></a>
+
+# ldap0r
+
+So far `ldap0r` is simply a very small web application just to reset
+LDAP passwords. An user enters its email address, receives an email
+containing a link to reset its LDAP password, thats it so far.
+
+
+<a id="org225ba27"></a>
+
+## Installation
+
+A rust nightly toolchain which can be aquired via <https://rustup.rs>
+is needed in order to successfully build `ldap0r`. Install `rustup`,
+download rust nightly, then clone this repository, set the
+toolchain inside the source directory to nightly, build and run it.
+
+    rustup toolchain install nightly
+    git clone https://git.onders.org/finga/ldap0r.git
+    cd ldap0r
+    rustup override set nightly
+    cargo run
+
+The application can be configured with the `Rocket.toml`
+configuration file.
+
+
+<a id="org54f2856"></a>
+
+## Todo List
+
+
+<a id="org09786dd"></a>
+
+### Password reset <code>[5/10]</code>
+
+1.  DONE Form to send resetlink
+
+2.  DONE Parse url with reset key
+
+3.  DONE Cleanup all unwraps
+
+4.  DONE Proper error handling
+
+5.  DONE Implement proper logging
+
+6.  TODO Make \`keys.lock()\` properly thread safe
+
+7.  TODO Check for existing keys
+
+8.  TODO Implement key validity timeout
+
+9.  TODO Implement proper tests
+
+10. TODO Optionaly store key persistently between restarts
+
+
+<a id="orgb93c7a2"></a>
+
+### Configuration <code>[0/5]</code>
+
+1.  TODO Fix domain config
+
+2.  TODO Make size of key configurable
+
+3.  TODO Make key validity timeout
+
+4.  TODO Make it possible to send emails over encrypted connections
+
+5.  TODO Make html/text emails configurable
+
+
+<a id="orga66a23f"></a>
+
+### Login Section (not sure if going to happen)