DB: Need to allow for longer network/station/location/channel codes

[megies]

Currently, the waveform database tables are fixed to a strict length of 2/5/2/3 for network/station/location/channel code, both for original and mapped codes (based on MSEED definitions).
We need to change this to allow for longer codes, since that is used in both some older data formats and also in some new data formats (MSEED v3).

Should be doable with a relatively simple DB migration (not sure if the table will have to be reindexed afterwards).

CC @jwassermann

jane/src/jane/waveforms/models.py

Lines 73 to 85 in 0dbbf9a

	class ContinuousTrace(models.Model):
	file = models.ForeignKey(File, related_name='traces')
	pos = models.IntegerField(default=0)
	network = models.CharField(max_length=2, db_index=True, blank=True)
	station = models.CharField(max_length=5, db_index=True, blank=True)
	location = models.CharField(max_length=2, db_index=True, blank=True)
	channel = models.CharField(max_length=3, db_index=True, blank=True)
	# Original codes for mapped ids.
	original_network = models.CharField(max_length=2, blank=True)
	original_station = models.CharField(max_length=5, blank=True)
	original_location = models.CharField(max_length=2, blank=True)
	original_channel = models.CharField(max_length=3, blank=True)