builder/parallels: 'ToolsIsoPath' added
builder/parallels: Added 'ToolsConfig' struct
builder/parallels: Added 'StepPrepareParallelsTools'
builder/parallels: Detect path to Parallels Tools ISO automatically.

'parallels_tools_host_path' param is deprecated
'parallels_tools_flavor' is added (mandatory).
builder/parallels: "guest_os_distribution" renamed to "guest_os_type".

"guest_os_distribution" become deprecated and is not required anymore.
But if it is defined (in outdated templates),then the value will be copied to "guest_os_type" and warning will be displayed.
website: Changed Parallels builder docs
Merge pull request #1455 from legal90/prl-tools-flavor

builder/parallels: Detect path to Parallels Tools ISO automatically