[evol] Librarian API work §3
[fix] Interface: intercept several possible errors around interface definition
[evol] API: implemented hidden nodes and used it to create a '?' node used to search children based on their attributes
[evol] allow splitting the API interface declaration over multiple files/directories, split MapMaker interface, and added cross-nodes storage during the interface life (as we can't use closures across files)
[fix] mistakes in API Interface: forgot to export node_name, and forgot :inspect is not available for nodes
[evol] server API tree reworked using a DSL (reply handling rework is WIP)
[layout] reorganization