Add a simple Python script to answer the question: should this NWB file be loadable by NWBE?

## Motivation
It can be difficult/time consuming to figure out whether an issue loading an NWB file in the online browser is down to the NWB file itself, a feature missing in NWBE, babdwidth issues etc.

## Proposal
Make a simple standalone script test_compatibility.py at the top level of this repo which can be run by `python test_compatibility.py MyNWBfile.nwb` which will test whether NWBE **should** be able to load the file. It should:

- Test to make sure the same versions of pynwb etc. as used by the full NWBE
- Print a short summary of some metadata (maybe just experimenter/description) and number of time series found in AcquisitionStimulus etc.

This can be used on a user's local machine for debugging issues. At a later stage it can be integrated into NWBE (on OSB) so that you can just type `test_compatibility(MyNWBfile.nwb)` into the python console to check if an NWB file in your workspace can be loaded (or just preview it).

Start with the proposed top-level test_compatibility.py entry point and inspect how this repository specifies the versions of pynwb and related dependencies. Run `python test_compatibility.py MyNWBfile.nwb` against an NWB file; done means the standalone script checks compatibility and prints metadata plus the number of time series found.

Written by the indexing model from the issue text.