Handle Merge Conflicts

[Conthrast]

If the user pulls a lib a certain version, then pull another block code that depends on the first version, but from an older version, this would be a merge conflict.

It should then have multiple features :

• Discard the current importation
• Downgrade the conflicted version if it does not create other conflicts
• Let the user update the current pulling by showing him the different modifications between the two versions

[PamplemomM]

Estimated time: 4 days