Listing custom functions

[gramian]

There is currently no way to list all custom functions currently available. So, I propose to add a special type to list those in the SQL context. For example this could look like:

SELECT FROM schema:functions

Given that custom functions are names by library.name, I think this type should consist of a library property of a string type library with the libraries name and a list property functions listing the library function names.
Alternatively, just a string property could be used holding library.string directly.

However, depending where the custom functions are scoped, visible and stored this could be named:

• schema:functions
• server:functions
• volatile:functions