Bulk of the Lunchbox code for #18: Move plugin functionality to Lunchbox
* Refactor Plugin wrapper to be more const and RAII-friendly
* Create distinct compressor and decompressor instance handlers
* Move PluginRegistry, CPU compressors and unit test from Collage to here
Add acknowledgements for CPU compressor base code
Changes needed for the Collage part of the plugin move (#18):
* Give (de)compressor handles a default ctor and move operator =
* Hide internal, augmented CompressorInfo from the API
API consistency (#18)
API cleanup (#18)
Minor fix for #18
Merge branch 'master' into plugins

Conflicts:
	lunchbox/CMakeLists.txt
Plugin code improvements for Equalizer porting to new #18 API:
* Add new down/uploader classes derived from eq::util::GPUCompressor
* Implement visitor pattern for PluginRegistry->Plugin
* Implement generic setZero() (aka bzero/memset)
* Create EqCompressorInfo ostream operator
Impl pattern for PluginRegistry (#18)
Fix calling the proper visit method during CompressorInfo traversal (#18)
Add missing files (#18)
Build fix (#18)
Fix built-in compressors (#18)
Merge branch 'master' into plugins
Merge branch 'master' into plugins
Merge branch 'master' of https://github.com/Eyescale/CMake into plugins
Merge branch 'master' into plugins
Adapt popBarrier API for OpenMP usage
Restructure GLEWContext usage for Downloader, which may have different ones for start and finish (#18)
Merge branch 'master' into plugins