improve console output to tell where the generated tests are

[monperrus]

When DSpot ends, it is written on the console Amplification results with 22 amplified tests.

However, the user does not know where to look ta the tests.

The message should tell where to look at the tests:

Amplification results with 22 amplified tests that are in 
target/dspot/........../FooTest.java
target/dspot/........../BarTest.java

[danglotb]

I improved the whole report procedure on test selector results, errors and output.

An example below:

[INFO] 2019-04-09 10:55:05 Main - Amplification succeed.
[INFO] 2019-04-09 10:55:05 Main - Elapsed time 8020 ms
[INFO] 2019-04-09 10:55:05 PitMutantScoreSelectorReport - 
Test class that has been amplified: fr.inria.sample.TestClassWithoutAssert
The original test suite kills 0 mutants
The amplification results with 2 new tests
it kills 56 more mutants

[WARN] 2019-04-09 10:55:05 ErrorReport - DSpot encountered some errors during amplification.
[WARN] 2019-04-09 10:55:05 ErrorReport - DSpot encountered 1 error(s) during amplification.
Could not find any test class that matches the given regular expression.
Your input:
	fr.inria.filter.failing.FailingTest
[INFO] 2019-04-09 10:55:05 OutputReport - The amplification ends up with 2 amplified test methods over 1 test classes.
[INFO] 2019-04-09 10:55:05 OutputReport - Print fr.inria.sample.TestClassWithoutAssert.java with 2 amplified test cases in target/trash/

The order is as follow, first, it outputs the result for each test class that has been amplified according to the test criterion, here one test class using PIT, then it outputs the errors encountered during the amplification, and finally, a summary of the result and where to find amplified test classes.

@monperrus WDYT?