YouTrack support for Harvest Time Tracker extension

This extension adds YouTrack integration for Harvest Time Tracker extension.

Functional:

1. Adds Harvest tracker button to ordinary issue view and agile issue popup
2. Adds one-way (H -> YT) time tracking synchronization\
   • works within 25 hours (syncs yesterday if triggered in first hour)
   • can be triggered by extension button
   • normally runs every hour automatically
   • if entry is in progress - tries to sync in 10 min
   • can update synced entries

Notes:

• For initial config see extension options
• Harvest entry notes should start with YouTrack issue id: XYZ-123
• YouTrack entry type can be set from Harvest task. Obviously, YT should contain it in list. "No Type" by default.
• YT work entry always will be set by current logged in user
• Entry will be updated each sync attempt (if changed), even if in progress
• Next planned date for sync is also available in the title of the extension button

In development:

1. Oauth2 support for Harvest
2. Refactoring and design