Verbose size

If option SIZE_VERBOSE will be enabled for target, cmake will print something like

```
AVR Memory Usage
----------------
Device: atmega32u4

Program:   19780 bytes (60.4% Full)
(.text + .data + .bootloader)

Data:       1949 bytes (76.1% Full)
(.data + .bss + .noinit)
```

This helps to understand, how much memory is left for code and how much RAM is available for stack.