Additional features for Custom Functions

[lvca]

This issue has been created from #288 as adding more features to Custom Functions.

• Allow executing a SQL script to make the registration easy at startup with a new setting arcadedb.startupScript. Example: -Darcadedb.startupScript=/temp/myscript.sql
• Custom Functions should be automatically published on HTTP if requested by the user (in the IDE a select field with ["no published", "HTTP get", "HTTP post"])
• Create a tutorial about writing a recommendation system by using a custom function

[lvca]

Moved to issue #1308