First round of updates from Jose.

LambdaLab/test/exercises/A_Lambdas.java

LambdaLab/test/exercises/C_DefaultMethods.java

LambdaLab/test/exercises/D_SimpleStreams.java

LambdaLab/test/solutions/A_Lambdas.java

LambdaLab/test/solutions/C_DefaultMethods.java

LambdaLab/test/solutions/D_SimpleStreams.java