Add "perl_maturity" option to release data APIs

[preaction]

The release data API presently only shows data from stable Perls. This makes it difficult to match up the data shown on (for example) MetaCPAN with the totals shown on every other site (which includes development Perls).

We have data from development Perls that we could give. Indeed, we used to already give this data (and that caused some problems like cpan-testers/cpantesters-web#10).

We should add a perl_maturity option. It should have three possible values:

• stable - the default, show only data from stable Perls
• dev - show only data from development Perls
• all - show combined totals from all Perls

All of the /release APIs should have this same parameter. For consistency's sake, the /summary APIs should also add the all value, which is the default for the summary APIs.