Refine gradient proto maker and python API for affine_channel_op

[qingqing01]

• Rewrite gradient ProtoMaker for affine_channel_op to remove the Output as the input.
• Add act in Python API to make the act can be in-place by layer_help.py

[sneaxiy]

LGTM.

[qingqing01]

[07:50:38]W:	 [Step 1/1] ++ python /paddle/tools/check_pr_approval.py 2 2887803 35982308 46782768 30176695
[07:50:38]W:	 [Step 1/1]   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
[07:50:38]W:	 [Step 1/1]                                  Dload  Upload   Total   Spent    Left  Speed
[07:50:38]W:	 [Step 1/1] 
[07:50:39]W:	 [Step 1/1]   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
[07:50:40]W:	 [Step 1/1]   0     0    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0
[07:50:40]W:	 [Step 1/1] 100  1783  100  1783    0     0    958      0  0:00:01  0:00:01 --:--:--   959
[07:50:40]W:	 [Step 1/1] + APPROVALS=FALSE
[07:50:40] :	 [Step 1/1] current pr 16340 got approvals: FALSE
[07:50:40]W:	 [Step 1/1] + '[' FALSE == TRUE ']'
[07:50:40]W:	 [Step 1/1] + echo 'current pr 16340 got approvals: FALSE'
[07:50:40]W:	 [Step 1/1] + '[' FALSE == FALSE ']'
[07:50:40] :	 [Step 1/1] You must have one RD (panyx0718 or chengduoZH or XiaoguangHu01) and one PM (shanyi15) approval for the api change! paddle/fluid/API.spec
[07:50:40]W:	 [Step 1/1] + '[' paddle/fluid/API.spec == paddle/fluid/API.spec ']'
[07:50:40]W:	 [Step 1/1] + echo 'You must have one RD (panyx0718 or chengduoZH or XiaoguangHu01) and one PM (shanyi15) approval for the api change! paddle/fluid/API.spec'
[07:50:40]W:	 [Step 1/1] + exit 1

@XiaoguangHu01 @shanyi15 Please help to review.

[shanyi15]

LG, comments