added 'nv_get_src_path' into common
added 'nv_get_arc_path' into common; nv_get_(build|arc|src)_path returns data in corresponding subdir in cache
nv: added migration for a new cache structure
added 'nv_get_system' into common; append cache type in 'nv_get_env_info_path';
fixed commands rm-cache/ls-cache
mk: added --force option; added optional 'plug_build' function
go-plugin: simplify
go-prebuilt plugin: added osx support; fixed sorting & building
elixir: used nv_get_src_path instead of nv_get_cache_full_path
julia: used nv_get_src_path instead of nv_get_cache_full_path; used https instead of ssh for github;
mk: added plug_fill_env function; added reset for plug_state
node-prebuild: added; fixes #5
elixir, julia plugins: fixed sorting
added tests for 'mk --force'
replace 'go' with 'go-prebuilt' in tests
added some comments into plugins
mk: remove unpacked src after inv created
added test for common:nv_get_system
added tests for node-rebuilt
mk: renamed plug_fill_env into plug_build_env