SSL support for push targets

[mp-se]

Add support for SSL. This should cover most targets.

Options:

• just skip cert validation. This is the easy approach and does not validate the remote target (if its valid). However it uses the least amount of memory and is easy to implement.
• use fingerprints to validate remote targets. this would require some type of function to catch and store the fingerprints for the remote targets and users will have to update when the remote certificate is updated. better security but not really user friendly
• store root ca in the device. this is the optimal solution but would require around 150 kb of flash storage to implement. There are projects that have done it but I'm not sure I want to waste this amount of space on certificates.

Need to investigate what the different libraries support.

[mp-se]

After some testing a full implementation of SSL is not going to work. Just loading the cert store with all root CA takes almost 3 seconds on a a device + 500ms to do the time synchronisation. This would kill the batterylife of the device. Will do some tests on ESP32 later to see if this is a better platform. I will focus on doing the simple approach for next release (option 1).

[mp-se]

dev branch now has support for ssl on http and mqtt targets.

brewfather and influx will be added if needed.