MCPL release 1.5.0

This release provides a few improvements concerning configuration of downstream projects. First of all, it introduces a new command-line script, mcpl-config which can be used to query an MCPL installation for details, or even used to setup the user environment by typing
eval $(./path/to/mcpl/installation/bin/mcpl-config --setup) in a shell. Secondly, it modifies the installed location of CMake configuration files, to hopefully make it easier for downstream projects to locate an existing MCPL installation (more details on github issue #58). Finally, it modifies the manner in which Geant4 bindings must be activated in downstream CMake code. In short, previous usage of find_package(G4MCPL) should be replaced with find_package(MCPL COMPONENTS GEANT4BINDINGS ), and the target G4MCPL::g4mcpl is now named MCPL::g4mcpl.