Use direct inclusion, not submodules, to bring Javelin into Phabricator

Summary:
Submoduling is slightly convenient for developers but hellishly difficult for many users. Since we make about a dozen updates to Javelin per year, just include the source directly.

Even if we run git submodule status more often, this creates additional problems for users with PATH misconfigured.

Fixes T2062 by nuking it from orbit.

Test Plan: Loaded site, browsed around. Grepped for references to submodules.

Reviewers: btrahan, vrana

CC: aran

Maniphest Tasks: T2062

Differential Revision: https://secure.phabricator.com/D4581