doc/format-analysis.org: 'info' textual fields in 'seg' features

Some external tools would like to provide sequence features with textual information.
Discussion with @flothoni and @duez.

doc/format-analysis.org

@@ -304,21 +304,24 @@ In the =.analysis= file, this section is intended to describe some specific clon
                      // Positions on the sequence start at 1.
       {
          "5": {"name": "IGHV5*01", "start": 1, "stop": 120},    // V (or 5') segment
-         "4": {"name": "IGHD1*01", "start": 124, "stop": 135},  // D (or middle) segment
+         "4": {"name": "IGHD1*01", "start": 124, "stop": 135, "info": "unsure designation"},  // D (or middle) segment
                      // Recombination with several D may use "4a", "4b"...
          "3": {"name": "IGHJ3*02", "start": 136, "stop": 171},  // J (or 3') segment
 
-                     // any feature to be highlighted in the sequence
-                     // the optional "seq" element gives a sequence that corresponds to this feature,
-                     // and the optional "val" element gives a numerical value.
+                     // any feature to be highlighted in the sequence, with optional fields related to this feature:
+                     //  - "start"/"stop" : positions on the clone sequence (starting at 1)
+                     //  - "seq" : a sequence
+                     //  - "val" : a numerical value
+                     //  - "info" : a textual vlaue
+                     //
                      // JUNCTION//CDR3 should be stored that way (in fields called "junction" of "cdr3"),
                      // its productivity must be stored in a boolean field called "productive".
-                     // Positions also start at 1.
-         "somefeature": { "start": 56, "stop": 61, "seq": "ACTGTA", "val": 145.7 },
+         "somefeature": { "start": 56, "stop": 61, "seq": "ACTGTA", "val": 145.7, "info": "analyzed with xyz" },
 
-                     // Numerical features concerning all the sequence or its analysis (such as 'evalue')
+                     // Numerical or textual features concerning all the sequence or its analysis (such as 'evalue')
                      // can be provided by omitting "start" and "stop" elements.
          "someotherfeature": {"val": 0.004521},
+         "anotherfeature": {"info": "VH CDR3 stereotypy"},
       }