buffer messages before writing to file

[But2ene]

Add two properties to the logging class
bufferMessages : The first is a cell array that contains messages to be
written.
bufferCursor_ is an integer that points to next cell to write in
bufferMessages_

During logging, messages are added to buffer. Once it's full, log lines
are written on file.

This new feature have no impact on logging on console.

A new method called setBufferingSize was created to change buffer size, on the model of the
others methods

[But2ene]

Hello,
here is a PR for a new feature to buffer messages before writing them,
it should give better performances in some cases.

I hope you find the style of code respected in this commit, and you find it usefull.
If so, I would be pleased if you accept it, so others that find this link on Matlab FileExchange can use it.

[dpo]

Thank you. Could you show in what circumstances this improves performance? I expect Matlab to already implement some sort of buffering.