Accept and handle various formats of peak flow data upload

• Open/read tab-delimited input files from local upload
• Open/read previously saved specification and input files from local upload
• Open/read multiple sites from a single input file
• Open/read multiple sites in a folder structure with one site per folder
• Allow users to enter a site number or list of site numbers for NWIS query
• Allow upload of WATSTORE files iff pointed to by older saved specification file