Merge pull request #3 from bjornstenqvist/master

multipole import
minor optimasation of dipole
Pair potential plus operator; Preliminary energy plus operator.
Documentation update; minimized dependencies; static assertions.
Merged tabulation code
Table integration; Geometry cleanup; Added tables and multipoles to
xcode.
Tabulate unittests
docs update and more unittests
deleted xcode user data
xcode cleanup
Merge pull request #1 from mlund/master

minor optimisation of dip-dip energy