Improve keys documentation.

MEMBERS.md

@@ -49,14 +49,30 @@ value and line number for further processing.
 Member File Processing - Pass 2
 -------------------------------
 
-Processed source is scanned for known keys.
+Processed source is scanned for known keys. Known keys are:
+
+* nick
+* name
+* mail
+* phone
+* born
+* joined
+* destroyed
 
 Multiple instances of single key are considered an error.
 
 Unknown keys are considered a warning.
 
 Valid multikeys are converted to single key with list of values and
-line numbers as the value for such key.
+line numbers as the value for such key. Multikeys are:
+
+* card
+* desfire
+* credit
+* studentstart
+* studentstop
+* suspendstart
+* suspendstop
 
 The result is a valid dictionary of keys and multikeys.
 
@@ -85,7 +101,16 @@ Credit list is parsed to get a list of amounts and optional comments.
 Member Record Finalization
 --------------------------
 
-If there is no ```'joined``` key, default month is substituded.
+If there is no ```'joined``` key, default month is substituted.
+
+If any of Mandatory keys is missing, it is filled with
+```#f```. Mandatory keys are:
+
+* nick
+* name
+* mail
+* phone
+
 
 Member File Schema
 ------------------