Feature/add jplag plagiarism detection

[JackSCarroll]

Depends on doubtfire-lms/doubtfire-api#447
Depends on doubtfire-lms/doubtfire-web#873
Feasibility document: thoth-tech/documentation#528

Description

Adds JPLAG container to docker-compose.yml. Container dockerfile and jplag jar file are located in ./jplag.

Type of change

Please delete options that are not relevant.

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas