PrimaryExpression and UnaryExpression are not decomposed

PrimaryExpression and UnaryExpression are not decomposed and this has a negative impact on the amount of memory used.

UnaryExpression should be

class UnaryExpression : AstNode
{
    Expression exp;
}

and then

class PrefixExpression : UnaryExpression {}
class PreIncrementExpression : PrefixExpression {}
class PreDecrementExpression : PrefixExpression {}
class AtExpression : PrefixExpression {}
class DereferenceExpression : PrefixExpression {}
class PostfixExpression :  UnaryExpression {}
class IndexExpression : PostfixExpression {}
class DotExpression : PostfixExpression {}
/**\ ETC \**/

For example a.b.c takes almost 3 kB of memory.

[WebFreak001]

this is one of my primary things that concern me about the current API layout, let's try to get this in before a 1.0.0 release!