Add/modify couple of commands into/in rtorrent config files

[chros73]

Add parameters for scraping intervals instead of being hardcoded (thx @pyroscope):

• cfg.scrape_interval.active for active downloads (~10 mins)
• cfg.scrape_interval.idle for idle downloads (~12 hours)

Add more commands into/in rtorrent config files (thx @pyroscope):

• d.session_file : the full path of the session file of a given download item
• d.get_ratio_float : d.ratio as float formatted string

Change current working directory to 'incomplete' dir in rtorrent config file (thx @pyroscope):

• system.cwd.set

Refactor couple of commands in rtorrent config files:

• hrf_time : it only formats a timestamp (no longer displays it)
• uptime: create a get_elapsed_time new method (Returns elapsed time between 2 timestamps) for it that can be used by itself as well
  • rename getUptime.sh external script to getElapsedTime.sh and remove the "Up:" word from it

Rename couple of commands in rtorrent config files:

• d.get_data_full_path -> d.data_path
• ui.messages.show -> pyro.ui.messages.show
• view.toggle_visible -> pyro.view.toggle_visible

Modify couple of commands in rtorrent config file (thx @pyroscope):

• s command
• purge command
• cull command

Add wrapper commands (thx @pyroscope):

• pyro.bind_key for scheduling key bindings
• pyro.view.collapsed.toggle to easily toggle a view
• pyro.collapsed_view.add to easily add new collapsed view