Improve IdList support in bindings

[fbergmann]

Description

This PR, ensures that calling IdList::at out of bounds throws an exception instead of crashing runtimes. It also adds some convenience wrappers for python to IdList: __len__, __iter__ and getitem`

Motivation and Context

fixes #306

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Change in documentation

Checklist:

• I have updated all documentation necessary.
• I have checked spelling in (new) comments.

Testing

• Testing is done automatically and codecov shows test coverage
• This cannot be tested automatically