Unclear findElement/findElementWithAssert import path

[ro0gr]

findElement and findElementWithAssert are currently exported from index.js and and extend.js.
Different import paths are also suggested in the docs for these helpers.

I feel importing it from ember-cli-page-object/extend is a recommended way but want to confirm first.
If so we should likely deprecate the other import path and fix the docs.

[san650]

The idea is to use the ember-cli-page-object/extend path. Let's deprecate the other export path!.

[ro0gr]

I think findElement/findElementWithAssert should be deprecated and removed from v2 in favour of new native DOM finder alternative.

Need a ticket for that new method(s) design.

[ro0gr]

finally #463