EDU-218 String index out of range: -1 on course reload when reloading a course

(cherry picked from commit 7c83ba23eb1ba4260acd8648989f593d79f56e0d)
cleanup

(cherry picked from commit 96238043d6a8918af7e5b6d79b3409cb8cf5ef2c)
EDU-228 Remove reload course action

(cherry picked from commit dcee9f02618d7198c9300db6d35cd05baaa2f5cf)
EDU-226 Rename Playground to Sandbox

(cherry picked from commit c72295cc2738659910d5233cde58a2fe26fb111c)
EDU-231 Move edit task window and delete task window actions to right-click menu

(cherry picked from commit 3d534f1c93bd697a7fa6d74f7e79688fc933caed)
EDU-230 Move show hint action to editor

(cherry picked from commit 01e1b8e689d8df1ba4a8763178a197dce6c27894)
EDU-182 Tell user to go to the next task window when show hint action is invoked outside of any task window

(cherry picked from commit 0232e6d8d6b312561758392324b8edeecb704a28)
EDU-237 Comment test_task_windows by default

(cherry picked from commit 96f696541f205ac6f756ef3779eb2e48b0bdc52c)
EDU-217 Close files from previous task when creating a new one - course creator mode

(cherry picked from commit 1031d47590e3ab53a174fe97838976d4c088682b)
added course creation project type icon

(cherry picked from commit 65f9d3ad452da92b918a2c32857e5b7908f2812f)
EDU-83 Add shortcut text to the next/prev/check button tooltip

(cherry picked from commit b9507243ef5500349be9e2116bbfbd250959fd33)
fixed EDU-245 More clear UI for creating task windows
(cherry picked from commit 5aba827)
fixed EDU-143 Add documentation comments to the test_helper.py

(cherry picked from commit e27fa74a68a5237c76f8d06482c3de4dfd31e1bc)
fixed EDU-190 Increace plugin versions

(cherry picked from commit 973acff4a85c009dbef247fa1fb92c63e8f57dbb)
fixed EDU-123 Plugin description

(cherry picked from commit 4bc73e45d07113d35af4a611e836afa662bb5d2e)
fixed EDU-200 Course creation dialog - text goes beyond the window

(cherry picked from commit 1f02a5cd89289ec4e559b9af7654d35909ed086a)
fixed wording
(cherry picked from commit 80bb2de)
updated course archive

(cherry picked from commit eb3f8b19800d58d24d4aa13b8a1b56f06f157893)
updated course archive

(cherry picked from commit a7a38b79ef65c866617bac3d6fac5eac31cac17c)
typo

(cherry picked from commit d77655240e8449668e71edc66fec78cff820618e)