Use libphutil script initializer to initialize scripts in Phabricator

Summary:
libphutil has some basic environmental sanity checks that we should use when initializing scripts in Phabricator. Principally this:

https://secure.phabricator.com/diffusion/PHU/browse/master/scripts/__init_script__.php;db643ee9f5f524e7$26

Without this, the default ini may set CLI errors to go to some logfile, which means exceptions aren't shown on stderr.

See https://github.com/facebook/phabricator/issues/98/

Test Plan:

• Ran "php -derror_log=/dev/null -f ./bin/phd debug adslkfnasdfnalks" prior to change; got confusing lack of output.
• Ran "phd -derror_log=/dev/null -f ./bin/phd debug asdkflnaslfdnala" after change; got exception on stderr.

Reviewers: btrahan, killermonk

Reviewed By: btrahan

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1950