Seperation of marking the sample for persistence and stubbing the sampled method

[rcschrg]

Currently we use the same API for marking methods and for creating stubs:
// Mark method so it can be used to record/load the method calls
Sample.of(testee.myTestMethod()); // no is/answer -> marked for persistence
Sample.of(testee.myTestMethod()).is("Hello World"); // creating stub to be returned when a real call appears. -> no persistence

This might be confusing when using both ways in a single test. So we should divide these apis to make transparent to the user what is happening.

[JanSchankin]

There is also a problem regarding the sequence of the Sample definitions. If manual Samples (non persistent) are defined before persistent samples are loaded from a file, the manual samples are lost. This is a recurring cause for confusion