[Core] Downloading files - Create solution for chunked files downloading

[Kuchasz]

• pause download
• resume download
• exposes informations about:
  • metadata file creation
  • download start
  • download progress
  • download speed
  • file size
  • download end
  • download finalisation (removing metadata file and changing data file extension)
• download one file with configurable number of concurrent connections
• support for server that does not expose APIs for chunked downloading using legacy HTTP/1.0 without concurrent connections and pause/resume features
• ability to set own extension for metadata files
• take care about performance, test it out on opi
• save file being downloaded to some kind of custom extension and create own metadata file that will contain data needed for download to resume