Represent declared type dimensions

[Gabriel-Darbord]

In typed languages, typed entities can be declared as arrays with dimensions:

int[] a; // 1 dimension
int[][] b; // 2 dimensions
int[][][] c; // 3 dimensions
int f() [] { ... } // 1 dimension, and yes the array brackets can appear after the parentheses in Java

We should add a dimensions field to hold the number of dimensions, which defaults to 0.
The field can be either be in FamixTTypedEntity, or in a new FamixTWithDimensions trait.
Since FamixTTypedEntity is currently used even for dynamic language entities, this may not be the right choice.