fix various JShint errors

app/AppInspector/app/store/Records.js
 * line 35  col 21  Duplicate key 'type'.

app/AppInspector/app/util/InspectedWindow.js
 * line 61  col 21  Unreachable 'break' after 'return'.
 * line 65  col 21  Unreachable 'break' after 'return'.

app/AppInspector/app/ux/data/proxy/InspectedWindow.js
 * line 17  col 19  'scope' is already defined.
CHEANGELOG added
CONTRIBUTING added
minor changes

 * property grid name columns are now 50% wide, instead of default 115px.
 * chrome.i18n only online available. fallback added.
 * highlight z-index set to 99999.
load-grunt-tasks module updateed

still can't update grunt-contrib-imagemin to 0.5.0 as it throws errors, have to wait for a fix
Merge pull request #56 from stoe/develop

JShint fixes, changelog, contributing & minor changes