Add and test sum of absolute values math functions for CPU and GPU
Add and test element wise sign math funtions for CPU and GPU
Instantiate caffe_cpu_sign for float and double
Add and test element wise abs math functions for CPU and GPU
Use macro to simplify element wise cpu math functions
Add and test non-in-place scale math functions for CPU and GPU
Add signbit math func, simplify GPU defs & instantiations with a macro
Rename signbit in macros to sgnbit to avoid conflicts with std::signbit
Fixed CPPLint errors related to math funtions
Merge pull request #201 from kloudkl/more_math_functions

Add more convenience math functions and all tests pass