Symfony5 implementation

[Alexandre-T]

This PR is fixing #69 and is now updated for symfony 5 :/

Because graphaware packages are no more maintained and their repositories were archived, I replaced graphaware/neo4j- by longitude-one/neo4j- packages. Be careful, if this package works with symfony 4.4 and symfony 5.0, it doesn't work anymore with symfony 2.8 nor symfony 3.4. So, you should create a new major version.

The longitude-one packages are only compatible with Neo4j ^3.0 package. Like GraphAware packages they are not compatible with Neo4j 4.0+ nor 4.1+ (not yet).

Jobs done:

• composer updated
• requiring longitude-one/neo4j- instead of graphaware/neo4j- packages
• phpunit.xml.dist updated to force the phpunit 8.5
• Fixing framework.yml
• travis updated to add test on php7.4 and symfony5 and to remove symfony2, symfony3, php5.6, php7.0, php7.1
• dunglas/symfony-lock replaced by symfony/flex in the travis.yml file

[mhitza]

Thank you for making these changes, helped me out.

I made a few additional changes in my fork that you could integrate in your PR.

Support for Twig 3.x: https://github.com/mhitza/neo4j-symfony/commit/1aabac576825c0b3911fcdd230fcbbac34b459ee https://github.com/mhitza/neo4j-symfony/commit/50589d14ac7c179094edc2183ee3a9b19ec72fe9 (the second change is incompatible unless Twig 1/2 are dropped, or a workaround is made)

Symfony kernel DataCollectorInterface type signature change https://github.com/mhitza/neo4j-symfony/commit/359eb1b5a7aecba9f43e58a1528a90f4346faa81

[nicodmf]

@neo4j-oss-build Can you review this PR, please ?