[2SP] Add C++ and message-based Edge API

[ivan-cukic]

Add the following to the Edge APIs (and make sure message-based and C++ Edge APIs have the same features):

• minBufferSize (exists)
• actualBufferSize
• a global connected that is true if both src and dst ports are connected (exists)
• weight (exists)
• edgeName (exists)
• nReaders() (new)
• nWriters() (new)
• edgeType() (Stream, Message)
• edgeMetaInfo().xxx() (based on the portMetaInfo() which should be identical for both src and dst port)

For edge ports - [input, output]Port() (possibly cached during the initial connection process):

• name()
• isSynchronuous()
• isOptional()
• priority()
• defaultValue()
• minSamples()
• maxSamples()
• available() (N.B. the only value that should not be cached)