Create getColumnRender, analogous to getFieldRender

Let Views use the same mechanisms as forms to render field values.
Use getColumnRender rather than the raw value

Also, lots of tidying and better names.
Use getColumnRender rather than the raw value (STATIC widget)

Also, lots of tidying and better names.
Still need to make the dynamic widget use this.
Merge branch 'jean-getColumnRender' of github.com:plomino/Plomino into jean-getColumnRender
Merge pull request #410 from plomino/jean-getColumnRender

Create `getColumnRender` method on view