…odeLocation #344

So far, the `sourceCodeLocation` of `JavaMember`s does not contain a line number, as it cannot reliably be inferred from the byte code (cf. #75).

However, if the class file contains a [`LineNumberTable`](https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.7.12) for a method, using the smallest line number from the `LineNumberTable` for the member's `sourceCodeLocation` – even if this probably corresponds to the first executable statement and not to the method header definition – seems to be more useful to me than using the fallback line number `0` in any case.

So for example, I would infer the line number `10` from the following byte code:
```
  void methodWithBodyStartingInLine10();
    descriptor: ()V
    flags: (0x0000)
    Code:
      stack=2, locals=1, args_size=1
         0: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
         3: bipush        10
         5: invokevirtual #3                  // Method java/io/PrintStream.println:(I)V
         8: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
        11: bipush        11
        13: invokevirtual #3                  // Method java/io/PrintStream.println:(I)V
        16: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;
        19: bipush        12
        21: invokevirtual #3                  // Method java/io/PrintStream.println:(I)V
        24: return
      LineNumberTable:
        line 10: 0
        line 11: 8
        line 12: 16
        line 13: 24
```
(My example's method header is actually defined in line 9, but I prefer 10 as opposed to 0... 😉)

Note that I do even get a line number for an empty method from the following byte code:
```
  void emptyMethodDefinedInLine15();
    descriptor: ()V
    flags: (0x0000)
    Code:
      stack=0, locals=1, args_size=1
         0: return
      LineNumberTable:
        line 15: 0
```

Even if line numbers inferred in this way do not exactly point to the method header definition, they can be used to  compare different methods (i.e., the ordering should be correct). This would allow for new rules like, for example (irrespective of whether I'd personally want to have them as arch rules or not):
* Public methods are defined _before_ private methods.
* `equals`, `hashCode` and `toString` are not generated by a framework (or a developer... 🙈) in the _same_ line (cf. #337)

With this pull request, line numbers are recorded for `JavaCodeUnit`s (`JavaMethod`s, `JavaConstructor`s, `JavaStaticInitializer`s) if the class file has a `LineNumberTable`.
(The reported line number `0` for `JavaField`s is unchanged, as it cannot be inferred from byte code.)