Get function's help infomation saved into a single file

Saves the help information of functions into a single file. This is sometimes useful when exploring

Save the help information in function files into a single file.

GetFunInfo(OutFile) saves the help information in function files under
the current directory into OutFile. This file will be created if haven't
done so and will be overwritten if exists.

GetFunInfo(OutFile,Functions) saves the help information in functions
specified in Functions into OutFile. Functions is a cell array and each element of the it is one function name.

Example:
>> GetFunInfo('FunctionInfo.txt');
Saves function information into FunctionInfo.txt

>> f = {'abs','sign'};
>> GetFunInfo('FunctionInfo.txt',f)
Saves information of functions abs and sign into
FunctionInfo.txt


Note that the output file is easier to read using wordpad than notepad under windows. Notepad tends to have word wrapping problem when displaying the text.