Enhance question service-frontend linkage

[chunweii]

Major changes:

• Standardize using c++ instead of cpp
• Remove "frameworks". The only valid languages now are python, java and c++
• Introduce default code for all 3 languages
• Introduce default list of topics to choose from
• Allow questions to be posted to question service
• Users can now update and delete their own questions
• Pagination works correctly

Changes to question service:

• Supports atlas search for title (can extend to have fuzzy search, but not important now)
• Start page is now 0-indexed
• GET /list now accepts body as a query param.
  • body includes the usual body parameters
• Only create one mongo connection
• Never close mongo connection (to prevent closing midway when other users are querying database)

TODO:

• Improve styling (eg. code editor for the defaultCode sections instead of text area)
• Fix issue with default code being populated again even after user deletes everything --> HELP WANTED
• Also, leading whitespace tends to get deleted in the text area, but we should allow whitespace --> HELP WANTED
• Filter by searchTitle, topics, difficulty --> HELP WANTED
• Delete directly from the table row?? (Low priority)