[NFR] FirePHP Log Adapter and Formatter

[ghost]

The idea was taken from the https://github.com/phalcon/incubator/tree/master/Library/Phalcon/Logger.

The adapter is meant to send messages to FireBug with FirePHP extension enabled.

This implementation differs from the incubator's:

• _initialized and _index properties are static — if by accident the user instantiates two loggers, FirePHP will be very confused;
• very long messages are split into 5KB chunks so that Firefox be able to read the headers properly.

Bonuses:

• much shorter version of Phalcon\Logger\Formatter::getTypeString()
• results returned by json_encode() are always NUL-terminated (otherwise Zend Engine complains loudly if PHP is built with debugging support)