Vagrant docs: added most awaited keys for VMX customisation
core: dup the synced folder options [GH-2134]
core: dup option hashes everywhere
Merge pull request #2127 from herdani/patch-1

website/docs: added most awaited keys for VMX customisation
website/docs: update vmx wordings
core: VAGRANT_VAGRANTFILE affects only project vagrantfile [GH-2130]
provisioners/chef: work with restrictive umask [GH-2121]
provisioners/puppet: sudo test for folders for umask
provisioners/chef: env config less restrictive