ConfigureKGTK should provide the ability to set SQLITE_TMPDIR

ConfigureKGTK should provide the ability to set SQLITE_TMPDIR. If SQLITE_TMPDIR is not set, Sqlite defaults to /tmp, which can be quite small.

@kyao please make the enhancement, Amandeep is on vacation

@kyao setting SQLITE_TMPDIR shouldn't be necessary anymore with recent updates, since now the tmp dir is set to be the same as the graph cache unless overridden by SQLITE_TMPDIR.