103 optimize channel and bandwidth of wireless network

[cbicari]

modded Puara so Default mode is now 20MHz.

Added API to set power threshold for broadcast, set and get wifi channels.
must be tested -- will most probably update the basic template to reflect these possibilities rather than random values in settings.json.

[edumeneses]

Looks good to me.

[cbicari]

ok so all functions are good and tested with following approaches :

Can be done anytime during runtime :
get_wifi_channels()
std::cout << "WiFi channel: " << static_cast(puara.get_wifi_channels()) << std::endl;

set_wifi_tx_power(wifi_power_threshold)
void onSettingsChanged() {
wifi_power_threshold = static_cast<int8_t>(puara.getVarNumber("WiFi_power_threshold"));
puara.set_wifi_tx_power(wifi_power_threshold);
}

---

Can only be done during setup as in [SAT mode cant do during connecting/scanning] and [softAP mode can't change if some STAs are connected] so setup triggered function won't work. ::
set_wifi_channels(wifi_channel_primary)

wifi_channel_primary = static_cast<int8_t>(puara.getVarNumber("Wifi_Channel_primary"));
puara.set_wifi_channels(wifi_channel_primary);

[cbicari]

We can now set/get channel and Tx power.
However channel can only be done during setup() routine and not in STA mode, and in AP mode only when no one else is connected..