added a documentation for the database structure

doc/database.md

@@ -0,0 +1,69 @@
+# Database structure
+
+## Used so far
+
+### pad:$PADID
+Saves all informations about pads
+
+* **atext** - the latest attributed text
+* **pool** - the attribute pool
+* **head** - the number of the latest revision
+* **chatHead** - the number of the latest chat entry
+
+*planed:*
+
+* **public** - flag that disables security for this pad
+* **passwordHash** - string that contains a bcrypt hashed password for this pad
+
+### pad:$PADID:revs:$REVNUM
+Saves a revision $REVNUM of pad $PADID
+
+* **meta**
+  * **author** - the autorID of this revision
+  * **timestamp** - the timestamp of when this revision was created
+* **changeset** - the changeset of this revision
+
+### pad:$PADID:chat:$CHATNUM
+Saves a chatentry with num $CHATNUM of pad $PADID
+
+* **text** - the text of this chat entry
+* **userId** - the autorID of this chat entry
+* **time** - the timestamp of this chat entry
+
+### pad2readonly:$PADID
+Translates a padID to a readonlyID
+### readonly2pad:$READONLYID
+Translates a readonlyID to a padID
+### token2author:$TOKENID
+Translates a token to an authorID
+### globalAuthor:$AUTHORID
+Information about an author
+
+* **name** - the name of this author as shown in the pad
+* **colorID** - the colorID of this author as shown in the pad
+
+## Planed
+
+### mapper2group:$MAPPER
+Maps an external application identifier to an internal group 
+### mapper2author:$MAPPER
+Maps an external application identifier to an internal author 
+### group:$GROUPID
+a group of pads
+
+* **pads** - object with pad names in it, values are null
+### session:$SESSIONID
+a session between an author and a group
+
+* **groupID** - the groupID the session belongs too
+* **authorID** - the authorID the session belongs too
+* **validUntil** - the timestamp until this session is valid
+
+### author2sessions:$AUTHORID
+saves the sessions of an author
+
+* **sessions** - object with sessionIDs in it, values are null
+
+### group2sessions:$GROUPID
+
+* **sessions** - object with sessionIDs in it, values are null