Sorts SYS.COMMANDS lexicograpihcally

Adds a proper sort order to SYS.COMMANDS as the current order is more or less random.

Rust update, Apollo and minor improvements

• Updates to Rust 1.51.0
• Extracts common functionality into Apollo
• Permits to register multiple loaders for a single repository file
• Extends the repository commands to support longer filenames
• Records the last error a loader reported and outputs it in REPO.LOADERS

Inner indices for IDB

Extends the way indices are computed for InfoGraphDB tables.

For a table like:

mappings:
    acme: test

We now support to add an index on mappings which will be used for a query like mapping.acme=test.