Add primitive types support for data object properties

It was defined that data modeller should support the use of primitive types to define/generate/read data object properties as well as the associated java.lang class.

In order to implement this the list of available types for an object property will be augmented with the primitive types.

The type selection list should look something like this:

BigDecimal <-- First: Java base types. (idem now)
BigInteger
...
...
Short
org.test.Pojo1 <-- Second: Objects defined in this model. (idem now)
org.test.Pojo2
ext- org.test.externalClass1 <-- Third: Object that can be references due to dependencies (idem now)
ext- org.test.externalClass2

short <-- At the end, the list of primitive types will be included.
int
long
float
double
byte
boolean