Small QOL improvement for osg_stats

Add partial_match and precision flag.

Sample output of osg_stats.py --stats _taken --partial_match --stats_sum --precision 6 s

source	key	number	min	max	mean	median	stdev	q95
s	lua_time_taken	1988	0.000000	0.000057	0.000006	0.000005	0.000004	0.000015
s	physicsworker_time_taken	1988	0.000000	0.005543	0.000442	0.000322	0.000431	0.001107
s	sound_time_taken	1988	0.000000	0.007465	0.000018	0.000006	0.000169	0.000042
s	mechanics_time_taken	1988	0.000000	0.005627	0.000231	0.000208	0.000181	0.000438
s	state_time_taken	1988	0.000000	0.000021	0.000001	0.000000	0.000001	0.000001
s	world_time_taken	1988	0.000000	0.005918	0.000530	0.000414	0.000463	0.001226
s	input_time_taken	1988	0.000000	0.014573	0.000176	0.000098	0.000415	0.000499
s	gui_time_taken	1988	0.000000	0.001447	0.000161	0.000132	0.000107	0.000340
s	script_time_taken	1988	0.000000	0.000868	0.000156	0.000142	0.000085	0.000303
s	physics_time_taken	1988	0.000000	0.000924	0.000036	0.000030	0.000031	0.000079
s	sum	1988	0.000000	0.014593	0.001758	0.001531	0.001135	0.003428