[NFR] - Dev mode and prod mode

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Applications can set to dev mode to enable development help message. Otherwise set to prod, with which applications only return 404/403/500 pages to user.

[adrlil]

Maybe when set to pro mode, phalcon can load some configuration and classes into memory and use them from memory directly. Otherwise set to dev mode, phalcon parse everything every request.

Interested in this issue please submit a full NFR following this guide https://github.com/phalcon/cphalcon/wiki/NFR to reopen this issue.