YT: https://youtrack.raccoongang.com/issue/EDX_BLND_CLI-87
- V2 libraries are available for selection in the Random Block edit modal;
- selected V2 library blocks are copied to the modulestore and saved as children of the Random Block;
- V2 library version validation works the same as for the V1 libraries (with possibility to update block with the latest version);
- filtering by problem type can't be done for V2 the same as for V1 because the v2 library problems are not divided by types;
- the problem type field is hidden for v2 libraries in the edit mode;
- unit tests added/updated.
- Moving xmodule folder to root as we're dissolving sub-projects of common folder in edx-platform
- More info: https://openedx.atlassian.net/browse/BOM-2579
- -e common/lib/xmodule has been removed from the requirements as xmodule has itself become the part of edx-platform and not being installed through requirements
- The test files common/lib/xmodule/test_files/ have been removed as they are not being used anymore
