Handle historical methods

[yiming-tang-cs]

For some methods which are in the git history but they have no corresponding methods in the current source code, they should be considered carefully to bump the DOI values.

Current source code:
Class p{
    m1(){…}
    m2()(…)
    m4()(…)
}

For example, each operation on the method will increase the DOI value of the method by 1 but decrease the DOI values of other methods by 0.5.

The interaction event history:
1. add m1()
2. add m2()
3. add m3()
4. modify m3()
5. delete m3()
6. add m4()

The DOI values:
m1(): 0
m2(): 0
m4(): 1

If we ignore m3(), the DOI values:
m1(): 0
m2(): 0.5
m4(): 1

[khatchad]

@saledouble How are you getting these numbers and are they decaying on their own?

[yiming-tang-cs]

I just use this as an example. The numbers are not important, and they are just used to show how their algorithm works. Actually, when I manually added a event into a task context, it would increase the DOI value of relevant method by 1.

For each time the DOI values is update, the decay is also computed. In the algorithm, SCALING(KIND-DECAY) is a constant. The value of decay is based on how many events from the fist relevant event to the latest events.

[khatchad]

Let's not use the algorithm but rather the the mylyn tool itself.

[khatchad]

As discussed, ignore these for now.

[khatchad]

Dupe of #98.