Fixes #310 - Linkify primary field

[bctiemann]

Fixes: #310

Introduces a render_table_column_linkified method on the base FieldType which during dynamic table generation is attached to the "primary" column and provides a "linkified" value which leads to the target Custom Object.

Upshot is that in a Custom Object list view table, the "primary" field (i.e. "name" below) is automatically made a link, making it easier to create a customized table view with clickable object names.

Note:
For all non-primary fields, custom column renderers (following the render_foo pattern of django-tables2) are still used for overriding the displayed value for multiobject, JSON, etc. Note that if a JSON or other formatted field is made the "primary", formatting will be lost due to the render_table_column_linkified behavior taking precedence.

[arthanson]

I'd argue that boolean, json, multi-object, object, multi-select, select should not be allowed to be primary name field, maybe run by Mark but (unless this was already discussed) but it seems strange and the loss of formatting just makes it more so.

If we do change this I'd suggest maybe re-arranging the edit form so "Type" field comes after name and depending on the toggle the "Primary name field" is shown or not (or disabled).