Add some tests

I was experimenting with some work-arounds to (what I see as) the problem of simple tokens being flagged as 'Recursion' too often.

In order to ensure I wasn't breaking existing behaviour, I have added a test suite that checks a number of expected behaviours.

I'll attach the test cases here.
Much of this could be done as unit tests also/instead, but WebTestCases are a bit more intuitive for what I'm looking at.

Run it as
drush test-run AETRecursionWebTestCase
or if you don't use drush
php scripts/run-tests.sh --verbose --class AETRecursionWebTestCase

Here are some of the relevant assertions it contains so far.

Pass      Other      aet.test           108 AETRecursionWebTestCase->testSingle
    Content from the token pulling body data from the target was found in the
    wrapper page when using token [aet:node:1:body]
Pass      Other      aet.test           109 AETRecursionWebTestCase->testSingle
    Using token [aet:node:1:body] did not trigger a recursive token warning.
Pass      Other      aet.test           116 AETRecursionWebTestCase->testSingle
    Using token [aet:node:1] did not trigger a recursive token warning.
Pass      Other      aet.test           117 AETRecursionWebTestCase->testSingle
    Embedded nodes title was found when embedding token [aet:node:1]
Pass      Other      aet.test           118 AETRecursionWebTestCase->testSingle
    Embedded nodes body was found when embedding token [aet:node:1]
Pass      Other      aet.test           125 AETRecursionWebTestCase->testSingle
    Using token [aet:user:2] did not trigger a recursive token warning.
Pass      Other      aet.test           126 AETRecursionWebTestCase->testSingle
    User history name was found when embedding token [aet:user:2]
Fail      Other      aet.test           156 AETRecursionWebTestCase->testSelfEm
    Node was able to embed its own title using a token [aet:node:1:title].
Fail      Other      aet.test           157 AETRecursionWebTestCase->testSelfEm
    Using token [aet:node:1:title] did not trigger a recursive token warning.
Pass      Other      aet.test           166 AETRecursionWebTestCase->testSelfEm
    Recursive token use was accurately detected
Pass      Other      aet.test           167 AETRecursionWebTestCase->testSelfEm
    Attempting to embed the body inside itself failed correctly when using token
    [aet:node:1:body].
Pass      Other      aet.test           215 AETRecursionWebTestCase->testCyclic
    Alpha node could embed the beta nodes title OK.
Pass      Other      aet.test           216 AETRecursionWebTestCase->testCyclic
    Recursive token use was accurately detected when creating an embed loop