ref(*): refactor chart/chartutil

ref(chartutil): move chart loading out of chartutil into new package
    add chart loader interface to allow lazy loading
feat(chart): create chart accessors
ref(*): cleanup requirements
ref(tiller): remove optional template engines
ref(tiller): simplify sorting releases and hooks
ref(*): code simplification
ref(hapi): move chart package out of hapi
ref(chart): add requirements and lock to Chart struct