Allow input files to have merge rather than replace in the web service

Means the workflow status checker will not overwrite input files with blank
Disallow launch-scheduled with wait which doesn't make sense and isn't tested
Remove deletion of input files from corresponding test
Merge pull request #118 from SeqWare/feature/SEQWARE_1750_input_file_overwrite

Feature/seqware 1750 input file overwrite