send Busy/Idle only from compute

and compute() is wrapped in Busy/Idle calls anyway
boost mpi fixes
run ctor when necessary
generate compile_commands.json for vim YouCompleteMe
improve loading of python module (vistle.py)

find python module based on executable location instead of relying on
PYTHON_PATH
clean shmem for specific vistle instance
show number of clients not capable of hybrid rendering
increase message queue size
make module launcher configurable by environment variables
beginnings of a distributed system

Hubs can connect to a master hub, UIs should connect to master hub,
parameter changes propagate between clusters. Data objects are not yet
forwarded.

This is still a work in progress, known problems:
- reduction (prepare/reduce module methods) does not work
- when removing modules, connections to those modules are not removed

And this might break a lot of other things as well...
IntVectorParameter & block/vertex indices of extrema
prevent recursive calls to parameterChanged
move cover config to vistle repo

also allow for loading IceT compositor from cover menu
adapt to our rhel7 installation