KSP Mod to add better antenna / link calculations to CommNet. Extends most CommNet classes.

The primary driver for this mod is to replace the KSP notion of an individual antenna having a "range" as a singular value that presumably derives from its gain and its transmission power. KSP's stock CommNet doesn't expose enough to change this behavior without replacing a few layers of classes.

The RealAntennas PartModule and its changes inside of CommNet implements a more detailed view of antenna & comms characteristics, such as antenna gain and transmit power; RF frequency, bandwidth and free-space path loss; some basic receiver noise modeling; and some elements from information theory (different modulation and encoding schemes, corresponding requirements for SNR (more precisely, Eb/N0), ultimately to provide variable data rates based on signal quality).

For those more familiar with the topic, it implements a typical link budget calculation: RxPower = TxPower + TxGain - FreeSpacePathLoss + RxGain. C/I or SNR = RxPower - Rx_NoiseFloor, with a variable threshold based on the modulation and encoding.

The current baseline implements a modulator for BPSK/QPSK/8PSK/QAM varieties. The C/I (or Es/No) is compared against minimum values to select the highest order modulation. Currently, there is only a model for digital communications.

Nodes (Vessels and ground stations) can have multiple antennas, each configured for a different band -- or even multiple antennas on the same band. At most one link is established between any pair of nodes, based on the best individual pair of antennas in each direction. Unlike stock, there is no combining of multiple antennas into a single unit, but you can achieve asymmetric links where the data rate in one direction is significantly different from the other.

I've spent a fair amount of time with the Unity Profiler to minimize any GC or runtime issues in RealAntennas. Please let me know if you encounter any performance-related issues that are tied to RA -- particularly if there is a noticable performance hit between RA and stock CommNet.