Handle preceding "@" in annotations

[kobylynskyi]

Possibility to provide custom annotation with and without "@":

• customAnnotationsMapping:

<customAnnotationsMapping>
    <EpochMillis>com.fasterxml.jackson.databind.annotation.JsonDeserialize(using = com.example.json.EpochMillisScalarDeserializer.class)</EpochMillis>
</customAnnotationsMapping>

<customAnnotationsMapping>
    <EpochMillis>@com.fasterxml.jackson.databind.annotation.JsonDeserialize(using = com.example.json.EpochMillisScalarDeserializer.class)</EpochMillis>
</customAnnotationsMapping>

• modelValidationAnnotation:

<modelValidationAnnotation>javax.validation.constraints.NotNull</modelValidationAnnotation>

<modelValidationAnnotation>@javax.validation.constraints.NotNull</modelValidationAnnotation>