refactor/tree_optimization

required for https://www.pivotaltracker.com/s/projects/896548/stories/55977048

### Pull Request Summary
<ul>
<li>Removed fancytree debugging
<li>Code refactoring & caching the DOM & fancytree object
<li>Added a selectionDidChange observer which updates the tree on changing the selection object
</ul>


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__General Requirements__
- [ ] Pull Request contains full description of changes
- [x] Link to the Pivotal Tracker story
- [ ] Pivotal Tracker story has a reference to this Pull Request
- [ ] Rebased against latest master branch
- [ ] All comments from code review have been addressed
- [ ] There are no `-1` code reviews (can only be overridden by Kyle)

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__Coding Standards__
- [x] Style guidelines are followed, code has been formatted
- [x] Code follows idiomatic language paradigms

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__Testing__
- [x] Test coverage has not decreased
- [x] There is no performance degradation
- [x] All appropriate automated tests are present
- [x] Appropriate seed data exists


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__Documentation__
- [ ] Major design decisions have been documented on the wiki
- [ ] Deployment impact (changes required for new services, configuration, etc.)
- [ ] documentation links from Pull Request

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__UI/UX__
- [ ] applicable (UI/UX has been changed)
- [ ] reviewed for usability and design
- [ ] functions on 1024*768 browser size
- [ ] works on IE8 (presently only required for SCiCustomer)

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__Defect__
- [ ] Feature or defect resolution has been manually tested and meets all requirements of the underlying story
- [ ] Seed data sufficient to satisfy testing resolution of defect
- [ ] Root cause analysis provided

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__Database__
- [ ] schema changes reviewed by Architect
- [ ] Excessive SQL queries are not generated
- [ ] Slow SQL queries are not generated unintentionally
- [ ] No DB schema changes are backwards incompatible
- [ ] Database schema changes documented on wiki
- [ ] Migration provided

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__Shared Project / Dependencies__
- [ ] Reviewed by Architect
- [ ] API changes to shared components documented on wiki
- [ ] 3rd-party library introduced:
- [ ] explanation for updating a project dependency (e.g. 'latest version fixes a bug')