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.
fix permission check
Merge branch 'staging' into 584-upload_button_permission_check
fix further poermission checks in the views (url maps)
fix failing test of url maps controller
add uri fetcher to fetch corresponding files

we can either fetch them to memory or directly
to the harddrive.
show only logics with ontologies as default
add check if an ontology is imported
make user_info a function
add ability to delete a file in a repository
add destroy route to an ontology
add controller actions to delete an ontology
add button to delete an ontology to view

tooltip is not shown yet because the according bootstrap javascript is not initialized
fix source target error
should fix #646
Merge branch 'staging' into optimize_complex_sql