Updated file logger

[DurieuxPol]

Updated MTAnalysisFileLogger with new file managing system.
You can use it like that:

analysis := MTAnalysis new
	            classesToMutate: { UUID };
	            testClasses: { UUIDTest };
	            logger: (MTAnalysisFileLogger toFileNamed: 'log.txt').
analysis run

[guillep]

Updated MTAnalysisFileLogger with new file managing system.

Haha! New! Since a couple of years already ^^

[guillep]

I like the formatting :)

[guillep]

Hi @DurieuxPol it should be better to put the delete in a tearDown method.
Otherwise, if the test fails for some reason, the system will remain dirty. (and the test will never pass then)

[guillep]

@inao0 will be interested in this PR.