show distance-to-home on position lines

Ignore-this: 217758c209729ab034564d99c17576ba

darcs-hash:20130910065632-312f9-79d7b34097857f0c631bd36fafb606f5afe26601
refactor positions list

Ignore-this: ba7ef74f574c36dfaf73658a0e75545d

darcs-hash:20130911061749-312f9-5bc83432be749276c78e905aaa234d9155fe97e0