minor #400 Updated some help notes for parameters.yml.dist (javiereguiluz)
minor #400 Updated some help notes for parameters.yml.dist (javiereguiluz)

This PR was merged into the master branch.

Discussion
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Updated some help notes for parameters.yml.dist

* Short params have been moved at the top of the file because `env(DATABASE_URL)` is too long and hides them
* `env(SYMFONY_LOG)` value is now wrapped in quotes to avoid deprecations
* Simplified `env(SYMFONY_SECRET)` description
* Commented the params related to the mailer (because the mailer is already disabled in the application)

Commits
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d44b8fe Updated some help notes for parameters.yml.dist

TomasVotruba/symfony-demo,jzawadzki/symfony-demo,vakstk50/jenkinstest,samitiana/symfony-demo,healthefrog/symfony-demo,Codeception/symfony-demo,voronkovich/symfony-demo,mrook/symfony-behat-codeception-demo,maidmaid/symfony-demo,yodur2potassium/test-behat-selenium-symfo,yceruto/symfony-demo,javiereguiluz/symfony-demo,mrook/symfony-behat-codeception-demo,voronkovich/symfony-demo,bocharsky-bw/symfony-demo,vakstk50/jenkinstest,yodur2potassium/test-behat-selenium-symfo,jzawadzki/symfony-demo,dzuelke/symfony-demo,maidmaid/symfony-demo,yceruto/symfony-demo,symfony/symfony-demo,healthefrog/symfony-demo,maidmaid/symfony-demo,javiereguiluz/symfony-demo,yceruto/symfony-demo,voronkovich/symfony-demo,javiereguiluz/symfony-demo,Codeception/symfony-demo,vakstk50/jenkinstest,nilamkhedkar1/symfony_demo,nilamkhedkar1/symfony_demo,TomasVotruba/symfony-demo,symfony/symfony-demo,jzawadzki/symfony-demo,bocharsky-bw/symfony-demo,samitiana/symfony-demo,Codeception/symfony-demo,dzuelke/symfony-demo,mrook/symfony-behat-codeception-demo,bocharsky-bw/symfony-demo,dzuelke/symfony-demo,symfony/symfony-demo,TomasVotruba/symfony-demo,samitiana/symfony-demo,nilamkhedkar1/symfony_demo,healthefrog/symfony-demo,yodur2potassium/test-behat-selenium-symfo