feat(tasklist): selectbox, radiobutton, textarea

Add support for the following form controls:

- <select> box for selecting a single value from a list of options.
  Supported datatypes string, boolean, number
  Options can be read form process variable (of type List or Map) or
  provided as constants inside form.

- <textarea> for editing longer text variables
  Supported datatypes: string

- <input type="radio"> for selecting an alternative from a list.
  Supported datatypes: string

related to #CAM-1388
feat(engine): support enum type in HtmlFormEngine

- support enum form type in HtmlFormEngine.
- enume is rendered as <select ...> box

related to #CAM-1388
Merge branch 'master' of github.com:camunda/camunda-bpm-platform