Investigate new mongo extension

[rexxars]

There seems to be a new mongo extension - the new one is called mongodb while the old one is mongo. I'm still a little unclear on the differences, but it seems like the old one won't be maintained in the future, so we should probably see if we can upgrade - especially if there is some sort of compatibility layer for the old extension.

[rexxars]

More info here: https://www.mongodb.com/blog/post/call-feedback-new-php-and-hhvm-drivers

[rexxars]

I've started investigating this in a branch: https://github.com/rexxars/imbo/tree/new-mongo

Got mostly everything working, database-wise. There is one bug in the official PHP driver that will be fixed shortly, which will fix the one test that is currently not passing.

I have not touched storage yet (GridFS) - not sure what the story is there, cause I see no classes for this so far. Will investigate further and possibly inquire if I can't find any more information.

[rexxars]

FYI: The reason why I've started working on this is that the old Mongo extension won't be updated to work with PHP7, it seems.

[rexxars]

For tracking purposes:

mongodb/mongo-php-library#57 - is required for GridFS
mongodb/mongo-php-library#78 - would clean up parts of the code where we translate between the objects returned and arrays to maintain backwards compatibility