Expand Python Snippet to support internal use cases

[aswallace]

The current version of the Python Snippet only supports external use cases (data read from csv, json or parquet and converted to strings). However, it should also support internal use cases, where data is read from the AICS database and has different types.

In the "Code Snippet" modal:

• Render the code to read data from AICS to pandas
• Add support for range filters and sorting on non-string types (e.g., date, date-time, numerical)
• Account for potential pandas type conversions: By default, pandas tries to make assumptions about dtypes when it creates a dataframe, which may conflict with our internal types.

Originally posted by @SeanLeRoy in #80 (comment)