fix: Manage template file when path is defined

[taorepoara]

About this PR

Closes #263

Technical highlight/advice

The upgrade command fails a lot. I've opened an issue for that: #403

How to test my changes

In a Lenra project that have a template file (.template):

• Move your lenra.yml file in the parent directory and define the relative path to your app directory.
• Then run the upgrade command

echo "path: ${PWD##*/}" >> lenra.yml
mv lenra.yml ../
cd ../
lenra upgrade

Checklist

• I didn't over-scope my PR
• My PR title matches the commit convention
• I did not include breaking changes
• I made my own code-review before requesting one

I included unit tests that cover my changes

• 👍 yes
• 🙅 no, because they aren't needed
• 🙋 no, because I need help

I added/updated the documentation about my changes

• 📜 README.md
• 📕 docs/*.md
• 📓 docs.lenra.io
• 🙅 no documentation needed