v1.8.0 - Major code fixes / cleanup

Major code cleanup and moved source to GitHub

• Fixed vulnerability (div0) with invalid DQT (thanks to Naf)
• Fixed vulnerability (DLL hijacking)
• Fixed compression stats for files with RST markers
• Fixes for batch file processing
• Fixed Photoshop 8BIM, XMP decode reporting
• Fixed command-line histogram output mode (-histo_y)
• Fixed command-line help for 'dhtexp'
• Fixed batch processing output with foreign characters
• Fixed batch processing with image decode option
• Fixed signature upload functionality
• Major code cleanup to eliminate warnings (Visual Studio 2017)

UPDATE 2018/10/02: Added v1.8.0a binary to address request in #41