* amend previous commit, fix runtime_error implementation
* Do not copy-construct classes that have a PBD::scoped connection list.
Replace std::map::emplace[C+11], an store shared pointers the std::map.
* Update ArdourMixerStrip is-a ScopedConnectionList (not has-a)
Use maps instead of vectors for holding strips and plugins
This allows to deal with "holes" after objects are removed
Also paves the way for a future improved way of identifying
individual strips and plugins
Terminology used by server and client was starting to diverge.
C++ classes ArdourStrips and ArdourGlobals classes have been
renamed to ArdourMixer and ArdourTransport respectively.
State node values for transport functionality have been simplified
and prefixed with 'transport_' to match what was done for strips.
