Assertion compilation fails when class has a template field

Generations plugin versions in maven:

```xml

org.assertj
assertj-assertions-generator-maven-plugin
2.2.0
```

Test class

```java
package testassertj;

import lombok.Data;

@Data
public class TemplateClassField {

protected T model;
}
```

Generated assertion class:
```java
package testassertj;

import org.assertj.core.api.AbstractObjectAssert;
import org.assertj.core.util.Objects;

/**
* {@link TemplateClassField} specific assertions - Generated by CustomAssertionGenerator.
*/
@javax.annotation.Generated(value="assertj-assertions-generator")
public class TemplateClassFieldAssert extends AbstractObjectAssert {

/**
* Creates a new {@link TemplateClassFieldAssert} to make assertions on actual TemplateClassField.
* @param actual the TemplateClassField we want to make assertions on.
*/
public TemplateClassFieldAssert(TemplateClassField actual) {
super(actual, TemplateClassFieldAssert.class);
}

/**
* An entry point for TemplateClassFieldAssert to follow AssertJ standard assertThat() statements.

* With a static import, one can write directly: assertThat(myTemplateClassField) and get specific assertion with code completion.
* @param actual the TemplateClassField we want to make assertions on.
* @return a new {@link TemplateClassFieldAssert}
*/
@org.assertj.core.util.CheckReturnValue
public static TemplateClassFieldAssert assertThat(TemplateClassField actual) {
return new TemplateClassFieldAssert(actual);
}

/**
* Verifies that the actual TemplateClassField's model is equal to the given one.
* @param model the given model to compare the actual TemplateClassField's model to.
* @return this assertion object.
* @throws AssertionError - if the actual TemplateClassField's model is not equal to the given one.
*/
public TemplateClassFieldAssert hasModel(T model) {
// check that actual TemplateClassField we want to make assertions on is not null.
isNotNull();

// overrides the default error message with a more explicit one
String assertjErrorMessage = "\nExpecting model of:\n <%s>\nto be:\n <%s>\nbut was:\n <%s>";

// null safe check
T actualModel = actual.getModel();
if (!Objects.areEqual(actualModel, model)) {
failWithMessage(assertjErrorMessage, actual, model, actualModel);
}

// return the current assertion for method chaining
return this;
}

}
```

Compilation fails on ` public TemplateClassFieldAssert hasModel(T model) {` method:

```
[ERROR] /C:/java/myproject/target/generated-test-sources/assertj-assertions/testassertj/TemplateClassFieldAssert.java:[37,44] cannot find symbol
[ERROR] symbol: class T
[ERROR] location: class testassertj.TemplateClassFieldAssert
```

**Expected behaviour:**
Generated assert class is also `` templated, so that `hasModel(T model)` compiles successfully.