test_xcamshift_a4 now works for all tests
test xcamshift vin now completes all tests
add code to initialise average to zero when averaging shifts

this doesn't seem to have an effect which suggests the array is being
cleared or initialised somewhere else...
add __len__ to Vec3_list for debugging

TODO: this class also needs a __getitem__ method
changes to make agaga test work

the problem was that new code was erasing the value of
_component_set['OFFS'] after it had been set by creating a new dict
correct code from verbose mode which was measureing the length of None
ensure shift caches are correctly created sized and cleared

including the fact the ensemble shift cache wasn't cleared between
rounds
add missing 'OFFS' entry to component to make tests work

not the test knows too much detail about the implementation of the non
bonded potential, however, this will have to be corrected later
update gb3 tests for ensemble based code
tests for ensemble gb3 only contain tests for ensemble code

note this code is not compatible with the main test suite as it requires
a properly constructed 2 member ensemble
corrections to test suite: test xcamshift was used called twice
add explicit instantiation of CDSString<char>
update to build scripts to make them more platform independent
add explicit template instantiation to xPyPot
add explicit template instantiation to pyEnsemblePot