Feature/fuzzy dates

Allow fuzzy dates to be specified for DateField widget

https://www.pivotaltracker.com/story/show/56777368

- Daterange widgets have a new attribute, 'allowFuzzyDates', to allow fuzzy (relative) dates to be stored in the 'fuzzyValue' property of the widget.
- When 'allowFuzzyDates' is true, a checkbox is added to the UI, which turns the fuzzy nature of the widget on and off.
- When the checkbox is on, fuzzy values selected from the dropdown are displayed in the field and stored in the 'fuzzyValue' property as-is (e.g. 'Tomorrow', 'year to Date'). This is particularly useful when used as a filter field, as the actual date will be re-calculated whenever the filter is evaluated.
- also here we remove some redundant files related to the filter panel


__General Requirements__
- [ ] Pull Request contains full description of changes
- [ ] Link to the Pivotal Tracker story
- [ ] Rebased against latest master branch
- [ ] There are no `-1` code reviews (can only be overridden by Kyle)

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__Coding Standards__
- [ ] Style guidelines are followed, code has been formatted
- [ ] Code follows idiomatic language paradigms

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__Testing__
- [ ] Test coverage has not decreased
- [ ] There is no performance degradation
- [ ] All appropriate automated tests are present
- [ ] 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

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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')

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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