Adding edge counter service and fixing some small bugs

[marcelomachado]

Fixes:

• Enabling edge filters by dataset.
• Fixed libraries versions as the deployment was compromised by updates to some libraries
• Fix to limiter fails #317
• Prepared api for Dockerizing

Features

• Provide a lightweight Dockerfile without PostgresSQL
• Add query/count endpoint that returns the number of edges based on a query (this supports Linked Data fragments interfaces such as TPF)

The fix and features can be tested using this docker image

I believe thir PR should bump a minor version (5.9.0)

Sorry for the mess. Although I should break it down into several PRs I think the changes are not that big and critical.