Introduce optimized recursive Graph-Stmt

Use a modified Version of the graph-data
query statement. Instead of looping
through by ourselves we use the PostgreSQL
recursive WITH Query to let the database do this for us

This increases the initial cost of the query but it scales
much more nicely when performing queries on much more
complex data or with a much bigger depth.
remove obsolete parts and make recursive default.
Determine GraphData cost for functions too

Although this might not be as useful, since
the calculated cost of functions is not such
a useful indicator for their cpu-cost.
add graph data function as a PostgreSQL function.
use compiled function for fetching graph data.
adding explanations as placeholder in the form
show only logics with ontologies as default
renaming issue related tabs
Merge pull request #645 from ontohub/596-renaming_repository_tabs

Rename tabs: "Ontology files and related files" to "File browser" and "Ontology URLs" to "URL catalog", fixes #596.
ilike_operator removed

We do not use MySQL any more.
Merge branch 'staging' into optimize_complex_sql
Return statements removed and some simplifications done.
"Cast" parsed URI to Boolean to avoid an explicit return of true.
Repaired OOPS global issues button.
implement pull request mentioned improvements
Merge pull request #643 from ontohub/595-explanations_for_upload_an_ontology_file

in the Team Meeting discussed
Extra script to start sidekiq.
Replace shellscript shell by sidekiq process.
Merge pull request #653 from ontohub/external-sidekiq-start-script

Extra script to start sidekiq.
Fixed entities controller test.