ModelAdmin is a little difficult to work with

[GuySartorelli]

ModelAdmin is a little clunky to work with at the moment - there are a few methods that don't require any instance data but aren't static, and any time you want to get a link for a managed model tab you need to re-implement the logic in sanitiseClassName() - and basically build the entire link from scratch every time with all of its component parts.

Acceptance Criteria

• Methods that don't need to be instance methods should be static.
• There should be an easy way to get a link for a managed model without having to reimplement sanitiseClassName().
• There is a straightforward way to get a canonical edit link for objects managed by ModelAdmin
• The changes are documented appropriately
• Documentation that currently includes re-implementing str_replace('\\', '-', $class) is updated

PRs

• NEW New API for managing models in ModelAdmin #1360
• MNT Don't require silverstripe/registry silverstripe-frameworktest#123
• DOC Document making ModelAdmin easier to work with developer-docs#83
• API Make some methods static for ModelAdmin #1355
• API Conform with changes to ModelAdmin silverstripe-versioned-admin#254
• DOC Document making methods static developer-docs#86

Related PRs

These are an extended approach for resolving the "There is a straightforward way to get a canonical edit link for objects managed by ModelAdmin" acceptance criterion

• NEW Add an extension to dynamically generate edit URLs #1361
• ENH Use the new CMSEditLink extension on SiteTree silverstripe-cms#2778
• DOC Document new CMSEditLink extension. developer-docs#85