Require Djblets 0.7.17.
Further lock down the generated Apache config files.

A security firm pointed out that .pht was a valid .php extension as
well, and that the SetHandler None didn't always turn off php. The new
config files now list .pht and other extensions in the list of file
extensions, and attempts to turn off the php module through php's
'php_flag engine off' directive.

The KB has been updated to include this, and to recommend turning off
any other Apache modules.
Release Review Board 1.7.13.
Merge branch 'release-1.7.x'