vyatta-cfg-vpn: move scripts/vtiIntf.pm to lib/Vyatta/VPN/vtiIntf.pm

Move vtiIntf.pm to a more logical place, in line with all the other
packages.
vyatta-cfg-vpn: update parseVtiTun to account for vti changes

Update the parseVtiTun function to account for the new way of
configuring VTIs.

Bug #358 http://bugzilla.vyos.net/show_bug.cgi?id=358
vyatta-cfg-vpn: update vti creation in line with changes to strongswan

Update the VTI creation process to go along with the changes added to
the vyatta-strongswan package, due to changes in the kernel vti module.

This also removes the need for additional netfilter rules to ensure that
packets are directed to the corresponding VTI.

Bug #358 http://bugzilla.vyos.net/show_bug.cgi?id=358
vyatta-cfg-vpn: reduce the vti mark base to prevent integer overflow

Reduce the vtiMarkBase value to prevent integer overflow on the created
ip xfrm states and policies.
vyatta-cfg-vpn: formatting changes for style consistency

Update lib/Vyatta/VPN/vtiIntf.pm to have consistent identation levels
and style throughout.