Added Scheduler UI and model

[Issue #24]
Scan form: Added crawl options

[Issue #24]
Scan form advanced options: Fixed markup

[Issue #24]
Scan form schedule options: Updated validation of day integers

[Issue #24]
Scan form: Tiny phrasing fix
Scan form schedule options: Updated structure

[Issue #24]
ScanManager: Updated to use the Scan Schedule

[Issue #24]
Scan: Removed debugging code
Scan _table_row: ONly list finished revisions
Scans: Added :started_at column
Scans revision nav: Added notice for scheduled revision

[Issue #24]
Scans: Allowed scan schedules to be editable

[Issue #24]
Scans: Can now be fully edited

[Issue #24]
Scans#show: Scan sidebar now updated via AJAX

[Issue #24]
Updated README

[Issue #24]
Scan form: Don't show advanced options for finished scans

[Issue #24]
Scan index: Updated edit buttons with a dropdown

[Issue #24]
application.js#restoreAccordions: Don't allow dups in cookie
Scan sidebar: Fixed flashing of buttons
application.js#restoreAccordions: Close open tabs inside closed accordions