Update the README file and minor change in CAVITE.

Signed-off-by: Cédric Hernalsteens <[email protected]>

README.md

@@ -23,3 +23,23 @@ pkg_resources.resource_listdir("zgoubi_metadata", "data/elements_yaml/")
 
 drift_yaml = pkg_resources.resource_string("zgoubi_metadata", "data/elements_yaml/DRIFT.yaml")
 ```
+
+## Definition of Zgoubi elements in YAML
+
+The [`YAML` format, https://yaml.org] ("YAML is a human friendly data serialization standard for all programming languages.") has been chosen for its simplicity and for its ability to be read from any other language. Great 
+libraries and support exists in `C`, `C++`, `Javasript`, many others, and of course `python`.
+
+Each Zgoubi element is defined in a `YAML` *document*. A `YAML` file consists either of a single (implicit) document or 
+of multiple documents. For simplicity, this repository describes each element in a separate `YAML` file with a single 
+implicit document. The document contains a mapping with the following keys:
+
+- **zgoubi_name**: the keyword of the element as defined by Zgoubi
+- **params**: the parameters of the element. See below.
+- **template**:
+- **cond_sections**:
+- **subelements**:
+- **doc**: 
+
+
+It contains a nested mapping. Each key is the name of a parameter while 
+the values are mappins 

zgoubi_metadata/data/elements_yaml/CAVITE.yaml

@@ -1,14 +1,14 @@
 zgoubi_name: CAVITE
 params:
-- IOPT: {type: E, unit: "", default: 0, doc: ""}
-- X: {type: E, unit: "", default: 0, doc: ""}
-- L: {type: E, unit: "", default: 0, doc: ""}
-- H: {type: E, unit: "", default: 0, doc: ""}
-- V: {type: E, unit: "", default: 0, doc: ""}
-- sig_s: {type: E, unit: "", default: 0, doc: ""}
+  IOPT: {type: E, unit: "", default: 0, doc: ""}
+  X: {type: E, unit: "", default: 0, doc: ""}
+  L: {type: E, unit: "", default: 0, doc: ""}
+  H: {type: E, unit: "", default: 0, doc: ""}
+  V: {type: E, unit: "", default: 0, doc: ""}
+  sig_s: {type: E, unit: "", default: 0, doc: ""}
 template:
-- - IOPT
-- - cond_section
+  - - IOPT
+  - - !!set {cond_section}
 cond_section:
 - key: IOPT
   equals: 0
@@ -18,7 +18,7 @@ cond_section:
 - key: IOPT
   equals: 1
   template:
-  - - L
+  - - !!str L
     - h
   - - V
     - X
@@ -43,4 +43,4 @@ cond_section:
     - h
   - - V
     - sig_s
-doc: |
+doc: |