Auryn 0.7.0-alpha with complex synapse support

The most important additions and changes are:

• Support for complex synapse models
• Added postsynaptic state traces to efficiently implement voltage based and calcium based plasticity models
• cmake for ease of building the code on multiple platforms
• Binary SpikeMonitor for increased simulation and analysis performance
• aube tool for decoding of binary spiking data
• Improved saving and restoring of network state in single binary file per rank
• Adds AdEx neuron model
• Adds auryn.h for cleaner import of the entire simulator package
• Improved doxygen documentation