Convert legacy projection syntax before applying

[alcaeus]

Fixes #144.

This was never properly documented in the driver, but has been there for quite some time. Digging into the code, I found the following comment (source):

Legacy handling where the projection is an array of field names to be included (e.g. ['x', 'y', 'z'] is converted to {'x': 1, 'y': 1, 'z': 1}).
This behavior dates back to 0.9.4, but there is no record of it in the extension's documentation. It should be deprecated/removed in the future, as it conflicts with supporting some legitimate projections (PHP-1056).

Thus, it's sensible to apply the same conversion whenever a projection is applied to a query.

[EmmanuelVella]

Just tested your fix, it's working great, thank you !

[alcaeus]

Thanks for the feedback, good to know!