corrected/changed DHCP-hostname generation and fixed compiler warnings

[walx666]

The generated hostname in dhcp.c is wrong formatted. The MAC-address bytes where inserted as binary values instead of a valid string format (ASCII).

The #define 'DCHP_HOST_NAME' was changed to "WIZ750SR-\0" (like WIZ107SR). A new function converts the MAC-address nibbles to hexadecimal ascii.

Hostname example with MAC-address = 00:08:DC:73:5B:25 orginal: "WIZnets[%" new version: "WIZ750SR-735B25"

I've also fixed all compiler warnings for App and Bootloader, where as the Bootloader-Code was not tested.

The version-number was increased to 1.4.1 and the development-state was added.