API Support react-router

[tractorcow]

Also adds breadcrumb view.

Merge with silverstripe/silverstripe-framework#5796

[sminnee]

@tractorcow we're still getting a test failure on this:

Using Jest CLI v0.9.2, jasmine2, babel-jest
 PASS  client/src/state/schema/tests/SchemaReducer-test.js (17.916s)
 PASS  client/src/state/gallery/tests/GalleryReducer-test.js (24.446s)
 PASS  client/src/state/editor/tests/EditorReducer-test.js (24.804s)
 PASS  client/src/state/queuedFiles/tests/QueuedFilesReducer-test.js (24.445s)
 FAIL  client/src/containers/Gallery/tests/Gallery-test.js
● Runtime Error
Error: Cannot find module 'react-router' from 'Gallery.js'
    at Loader._resolveNodeModule (/home/travis/builds/ss/asset-admin/node_modules/jest-cli/src/HasteModuleLoader/HasteModuleLoader.js:431:11)
    at Object.<anonymous> (/home/travis/builds/ss/asset-admin/client/src/containers/Gallery/Gallery.js:7:46)
    at Object.<anonymous> (/home/travis/builds/ss/asset-admin/client/src/containers/Gallery/tests/Gallery-test.js:12:42)
1 test suite failed, 30 tests passed (30 total in 8 test suites, run time 35.997s)

[tractorcow]

I'm looking into this now.

[tractorcow]

I've pushed up a fix... tests should be passing now. :D