Replace workflow tasks board with activity statuses overview

[MiroDojkic]

This PR:

• replaces tasks with activity statuses
• replaces board view with overview table

Config changes:

• each activity status should define color property
• dueDateWarningThreshold should define how long before the due date should the warning about upcoming due date be displayed

Example of partial config with workflow:

module.exports = {
  SCHEMAS: [{
    id: 'SCHEMA_ID',
    workflowId: 'WORKFLOW_ID',
     structure: [{
      type: 'COURSE',
      label: 'Course',
      color: '#0a1747',
      rootLevel: true,
      subLevels: ['LESSON'],
      isTrackedInWorkflow: true
    }
  }],
  WORKFLOWS: [{
    id: 'WORKFLOW_COURSE',
    statuses: [
      { id: 'TODO', label: 'Todo', color: '#f7fff7', default: true },
      { id: 'DRAFT', label: 'Draft', color: '#ffe66d' },
      { id: 'REVIEW', label: 'Review', color: '#ff6b6b' },
      { id: 'READY_TO_PUBLISH', label: 'Ready to publish', color: '#4ecdc4' },
      { id: 'DONE', label: 'Done', color: '#1a535c' }
    ],
    dueDateWarningThreshold: { days: 2 },
  }]