Added support for array filters

[gtsiam]

Changes:

• Added support for array filters.
• Derive Clone for Client

Notes: I changed the with_filter method to require an impl Into<Filter<'a>>. This should both allow writing custom filter types for building more complex queries and, for some of the simpler cases, to simply pass in a few Vecs to get it to "just work". Another notable change, is that the string part of the filter now uses Cow, as I quickly run into issues in my project with ownership when building more complex queries.

Fixes #217 Fixes #163