[debian8] remove workarounds: bug fixed in 2.5.4~rc7-1
[debian8] remove double apt-get update
[kameleon] rename centos6.5 -> centos6
[debian8] add OAR_APT_OPTS to OAR apt-get commands
[centos6] rename vagrant base box -> centos6
[misc] add vagrant-snapshot.sh: snapshoting all VMs at once
[misc] vagrant-snapshot.sh -> cosmetic enhancemnet for list
Merge branch 'devel' into oar-2.5.2

Conflicts:
	deb_debian8_pgsql/provision.sh
[debian8] finish merge, add $OAR_APT_OPTS -> apt-get commands