Large rework for 1.5 goals

Large rework to obtain features planned for 1.5:
- new encoding pipeline: container->format->codec->tool
- ability to use several codecs at once
- support for ETC1 compression. 4 tools: AtiCompress (which is really an
older etcpack), Etcpack 2.72, Rg-Etc1, PvrTex - PowerVR SDK tool)
- support for PVRTC compression with PowerVR SDK tool
- CrunchLib, PvrTex tools for DXT codec
- quality/speed profiles (-fast, -regular, -best). Regular is default.
- BGR6 BGR3 BGR1 formats for BGRA codec (stores Alpha in 24-bit image)
- bugfixes
- drag&drop decoding of compressed files
- drag&drop encoding for multiple files
- new key -t (packs & unpack to separate suffixed file)
- new keys -stf/-st/-sf (adds file suffix related to codec/tool used)
- preliminary support for KTX format
- new options file syntax with specific options for codec/tools