Remove Large.json from project, copy while running tests

[bwhiteley]

The file Large.json causes projects which use Marshal to slow down Xcode while searching for strings.

This patch removes Large.json from the project and adds a build phase to copy it so that it is available for the performance test.

[jarsen]

Looks good, but has a merge conflict since I just merged a commit also fixing tests. I'm ok merging this once it's rebased.