Evaluate data loaded by MAVEN sta() (STATIC) load routine, to see if it's possible to write a mvn_part_products routine around it

[jameswilburlewis]

I've changed the sta() load routine so that if no datatype is specified, it loads all available data. There are quite a few variables that seem to have angle and energy tables (and hopefully the actual distribution data), so maybe there's enough there for us to make moments, spectrograms, slices, etc.

Here's a sample call from our test suite:

    def test_load_sta_data(self):
        del_data("*")
        # No datatype means "load everything"
        data = maven.sta()
        self.assertTrue(data_exists("hkp_raw_2a-hkp"))
        self.assertTrue(data_exists("hkp_2a-hkp"))
        self.assertTrue(data_exists("data_d0-32e4d16a8m"))
        self.assertTrue(data_exists("theta_d1-32e4d16a8m"))
        time.sleep(sleep_time)