docs($compile): improve transclusion documentation

Closes #9352
test($compile): add test for alternative syntax to get controllers from ancestors

Because the regex that tests the `require` value will match more than just `^^?`,
it is important to test other common ways to specify a controller requirement
to ensure that a breaking change isn't introduced inadvertently. This adds a test
for `?^^`.

Closes #9389
Closes #9390
docs(CHANGELOG.md): update 1.2.26 release name
fix(form): fix submit prevention

Do not prevent submit when action
attribute equals to an empty string.

Closes #3370
Closes #3776
perf(ngBind): set textContent rather than using element.text()

"Speeds up chrome with ~10% firefox by ~5%"

We don't really see this result in benchmarks (https://www.dropbox.com/s/76wxqbvduade52s/big_table_benchmark_b1ee5396_vs_d580a954.zip?dl=0)
However, it's basically harmless.

Side effects:

Use strict equality check for `undefined` to replace with empty string. Most target browsers will output `undefined` rather than the empty
string if we don't do this. Previously, ngBindTemplate did not perform this check. However the change has been made to make behaviour
consistent across all target browsers (chrome does output the empty string).

Closes #9369
Closes #9396
fix($location): allow 0 in path() and hash()
chore(release): create script to undo a release for given number