[Compiler] Add support for arrays

[kmruiz]

Right now, neither the ANTLR4 parser nor the code generator support array types. Array types can be from any other basic type, but there are two constraints:

• Array types from other basic types (like int or char) can contain default values in the form of:

int[] array = {1, 2, 3}

• Array types from other complex types (like other types already created through schemata) can not contain default values.

How to implement

• Add support for the array syntax to the lexer: src/main/antlr4/io/vlingo/schemata/codegen/antlr/SchemaVersionDefinitionLexer.g4
• Add support for the array syntax to the parser: src/main/antlr4/io/vlingo/schemata/codegen/antlr/SchemaVersionDefinitionParser.g4
• Change the FieldDefinition for adding support to ararys: io.vlingo.schemata.codegen.ast.FieldDefinition
• Change the JavaBackend to support arrays: io.vlingo.schemata.codegen.backend.java.JavaBackend

[VaughnVernon]

@kmruiz Correct. From the spec the arrays of complex types are not expected to support initialization:

category.TypeName:1.2.1[] typeNameArrayAttribute1