add methods needed by SWIG to fallback string class [thanks elen4]
yarp::os::impl::Election -> yarp::os
remove last straggling ::impl uses in carriers+modules
fix stray PeerRecord::iterator use
Print the reason why an external package is being compiled
Unset cached variable instead of making it INTERNAL

This should fix YARP_USE_SYSTEM_XXX not appearing after installing
a library.
Fix typo in c7f6aefb7e1a665eede30a88e10e18dc93f77349
Do not cache the variables for libraries in extern
Fix some logic in searching for dependencies

Also add variables YARP_HAS_SYSTEM_XXX for each dependency
updated deb build script to manage correct version
Make print_dependency messages a STATUS message
stubs
add stub for Node + Nodes
add stub test
add mutex
basic store of contactables in node
add auto-generated node ports
stubs for slave api
basic type propagation
switching over to use of real nodes