[V4CC][NEW] KVC for VCursor and VTable.

In v4.8 we adding support of Key Value Coding (KVC) to VCursor and VTable classes.

This is implemented as VCursor (KVC) category with a couple of methods:

@interface VCursor (KVC)
                // If wrong key is specified then nil is returned.
- (id)		valueForKey:(NSString *)key;

                // If wrong key is specified then nothing is changed.
- (void)	setValue:(id)value forKey:(NSString*)key;

As a key is used a field name of the cursor. As a value is used a VField.Value of that field.

It is easy to see that these methods are just wrappers to existed V4CC methods. In general, valueForKey is implemented as:

VField* fld = [myCursor fieldForName:inName];
id value = [fld value];

For details please check sources of V4CC_Cursor.KVC.mm file. In reality, valueForKey do more accurate job for Pictures and Binary fields.

So it is obvious that these KVC methods give us at least two advantages:

a) we enable VCursor/VTable classes to major Cocoa technology KVC, which is widely used.
b) you self can use these methods to simplify your code.