When one use Monolog in a long process like an AMQP worker with a
`FingersCrossedHandler` or `BufferHandler` there is a drawback: as soon as there
is an AMQP message that generate a log >= error (for example), all next AMQP
messages will output logs, even if theses messages don't generate log where
level >= error.
In the same context there is a drawback for processor that add an UUID to the
logs. The UUID should change for each AMQP messages.
---
This patch address this issue with a new interface: `ResettableInterface` interface.
Side note: `reset()`, `flush()`, `clear()`, are already used in Monolog. So
basically, one can use the `reset()` on the `Logger` and on some
`Handler`s / `Processor`s.
It's especially useful for
* the `FingersCrossedHandler`: it `close()` the buffer, then it `clear()` the buffer.
* the `BufferHandler`: it `flush()` the buffer, then it `clear()` the buffer.
* the `UidProcessor`: it renew the `uid`.
This handler can be used to not let any messages from a certain lever through, unless they cross a configured threshold.
This is useful together with, for example, a MailHandler when some batch processing is done and you're only interested in
major failure and not a minor one.
When making the calculations for the filename of the current month using
date('d') does not work because you may run into the situation where you run
the tests on a day in a month that does not exist in the previous month,
for example March 30th. As there is no February 30th, PHP will skip ahead
to March, and the filename for the "previous" month will incorrectly be
"2017-03" instead of the expected "2017-02". Using the first day of the
month instead of the current day of the month solves this problem.
For consistency we now also use the first month of each year for calculations
regarding years even if this is not necessary, it would break symmetry
if we don't, plus it makes it clear that the value is not relevant in the
calculation.
