Tasks screen improvements

Summary
========

1. Make improvments to the tasks screen.
2. Follow OpenStack Horizon look and feel.

Motivation
========
1. Missing functionality in the tasks screen.

Mock
====
Needed!

Description
=========
Implement the following GUI:
1. Tasks list
  a. Columns are:
    * ID - Link to open task Overview
    * name – task name
    * execution id - Link to execution overview screen
    * result– link to a modal that shows the "result" data (currently exists in the api).
    * published – opens a modal that shows the "published" data (currently exists in the api).
    * created at
    * updated at
    * state
  b. Sort allowed by ID, name, created at, updated at, state, workflow name. Default sort by "updated_at" DESC
      client side sorting until API v3)
  c. Filter by executionId (server side) and state(client side).

2. Task overview
Shows the following info:

   * name – task name
   * execution id - Link to execution overview screen
   * result – shows the "result" data(currently exists in the api).
   * published – shows the "published" data (currently exists in the api).
   * created at
   * updated at
   * state

3. Auto refresh the entire screen

Outside Dependencies
==================
API calls are supported (Mistral base API):

1. task-list
2. Task-get
3. Task-get-published
4. task-get-result

Doc Impact
=========
1. Add explanation to the new UI elements
2. Add explanation to the new flow