Update sched_e MV to support sort on non-standard s_o_ind value

[fecjjeng]

While implementing fec-cms issue #2494 Support/Oppose sort on IE table not functioning
fecgov/fec-cms#2494
It had been noticed some rows with s_o_indicator 'unknow' in the front-end always shown on top, despite sort null first or null last. After further investigation, it is revealed the s_o_ind column has non standard (should be 'S' or 'O' or NULL) value which caused the problem. It need to be handled in the data level.

[] Update ofec_sched_e_mv to support sort on non-standard s_o_ind value

[fecjjeng]

The problem is s_o_ind column includes values that are not standard 'S' and 'O', which offset the sorting.
"0";3
"A";35
"O";438620
"S";621794
"SUP";37
"UNI";188
"";101749

The sorting is on s_o_ind, not the description. The description displayed in the front end is controlled by cms code, not database, based on the database value in the s_o_ind column. In order to make the non S/O rows sorting correctly, we will need to change the value in the s_o_ind column in the MV. It had been agreed that we will replace all the non S/O values with null in the s_o_ind column. This way we can handle all the strange values yet to come, and no additional cms changes needed.

[fecjjeng]

PR #3533 had been merged to DEV.