Group index table check API

Signed-off-by: leo-ma <begeekmyfriend@gmail.com>

This debug API will print mib group index table information through generator checking whether it can be inquired correctly by snmp get/getnext command. The usage is as follows:
```
mib.group_index_table_check(group, 'name')
```
Single indexes:
```
Group 'ifGroup' index table:
scalar indexes:
Dim1:
1
Dim2:
0
table indexes:
Dim1:
2
Dim2:
1
Dim3:
1	2	3	4	5	6	7	8	9	10	16	22
Dim4:
1	2	3	4	5
```
Long indexes:
```
Group 'tcpGroup' index table:
scalar indexes:
Dim1:
1	2	3	4	5	6	7	8	9	10	11	12
Dim2:
0
table indexes:
Dim1:
13
Dim2:
1
Dim3:
1	2	3	4	5
Dim4:
0	0	0	0	22	0	0	0	0	0
10	2	12	229	33874	91	189	92	10	443
10	2	12	229	33875	91	189	92	23	443
10	2	12	229	37700	180	149	153	11	80
10	2	12	229	46149	180	149	134	54	80
10	2	12	229	53158	123	58	181	140	80
127	0	0	1	631	0	0	0	0	0
scalar indexes:
Dim1:
14	15
Dim2:
0
```
Cascaded indexes
```
Group 'ThreeIndexTable' index table:
table indexes:
Dim1:
1
Dim2:
1
Dim3:
1	2	3
Dim4:
1	3	5	7
Dim5:
2	3
Dim6:
32	87	123
```