workflows: holdingpen details page improvements

* Adds 2 new stages for workflow objects error and waiting.

* Better display of workflow definition.

* Display of completed tasks.
Please choose 2 (or 4) spaces for indentation consistently in one module.

#### Vim Trick 
```
:filetype indent on
:set filetype=html           # abbrev -  :set ft=html
:set smartindent             # abbrev -  :set si
```
and then `gg=G`

@tiborsimko or *Google*  might give you an example for other editors (e.g. Emacs)