To evolve Docker image to integrating Graal module

[florentk]

https://github.com/chaoss/grimoirelab-graal is a Generic Repository AnALyzer for Grimoirelab. He uses among other things coloc or lizard tools.

The actual docker don't include the Graal integration but a first version of this integration is proposed as a fork here (see docker subdirectory) based on the work of inishchith at Google Summer of code 2019.

Graal integration allow to add a new dashboard to show metric :

• Total line of code (LOC)
• Total line of comment
• Total number of function
• Code complexity
• Comments per LOC
• LOC per function
• Statistics on file extension