hawc2.htc: do not lower string values when reading from HTC file

Do not convert all values read from the htc file to lower case. Only two tests had to be modified, but we'll have to see if any other edge cases might need some additional attention.

This is necessary for example when reading a master file that contains tags that contain upper case characters. Also for the future HAWC2 linux versions for which file names become case sensitive this might be important.