Added docs as asciidoctor with cross platform support. (#5733)

* Added docs as asciidoctor with cross platform support.

* Fixed release script with new doc building mechanism.

doc/database.adoc

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+== Database structure
+
+=== Keys and their values
+
+==== groups
+A list of all existing groups (a JSON object with groupIDs as keys and `1` as values).
+
+==== pad:$PADID
+Contains all information about pads
+
+* **atext** - the latest attributed text
+* **pool** - the attribute pool
+* **head** - the number of the latest revision
+* **chatHead** - the number of the latest chat entry
+* **public** - flag that disables security for this pad
+* **passwordHash** - string that contains a salted sha512 sum of this pad's password
+
+==== pad:$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 chat entry with num $CHATNUM of pad $PADID
+
+* **text** - the text of this chat entry
+* **userId** - the authorID of this chat entry
+* **time** - the timestamp of this chat entry
+
+==== pad2readonly:$PADID
+Translates a padID to a readonlyID
+
+==== readonly2pad:$READONLYID
+Translates a readonlyID to a padID
+
+==== token2author:$TOKENID
+Translates a token to an authorID
+
+==== globalAuthor:$AUTHORID
+Information about an author
+
+* **name** - the name of this author as shown in the pad
+* **colorID** - the colorID of this author as shown in the pad
+
+==== mapper2group:$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 1
+==== 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
+
+* **sessionsIDs** - object with sessionIDs in it, values are 1
+
+==== group2sessions:$GROUPID
+
+* **sessionsIDs** - object with sessionIDs in it, values are 1