Updated PID file location to come from configuration

Partial fix for #2103 where on _NIX platforms the PID file location is hardcoded.
Now it will try and use the PID file defined in `./conf/neo4j-wrapper.conf`, or fallback to the current default of `./data/neo4j-service.pid`.
Make the PageCacheTest less flaky

I have not been able to reproduce the flakiness locally, so it's just guesswork if this change helps.
Cleanup idSeekLeafPlanner
Browser: reverse arrow deflection based on direction.
Browser: fix arrow shaft breaks for positive deflection.
Merge pull request #2862 from chrisvest/2.2-less-flaky-pagecache-test

Make the PageCacheTest less flaky
Add hidden config to disable pin/unpin monitoring
Document time unit used for timeout in javadoc.
Don't restart force layout on resize.

Choose arbitrary fixed dimensions (200 x 200) for the force layout,
then use SVG viewBox to keep the fixed range centered.
This means that we don't need to tell the D3 force layout when the
visualisation changes size. It avoids the distracting drift when,
for example, opening and closing the side tabs. Also makes the position
of fixed nodes more consistent with the centering gravity force.
Merge pull request #2868 from chrisvest/2.2-hidden-config-for-pagecache-pinunpin-monitoring

Add hidden config to disable pin/unpin monitoring
Fix races on shutdown in Muninn

The Muninn eviction thread did not anticipate that closing the page cache would
set all the MuninnPage references in the `pages` array to `null`, and so it
could die with a NullPointerException.

It now interprets the precense of a `null` value as a signal to shut down.
fix: update labels/attributes when viz is updated
Increase font-size in footer
Fix footer in FireFox
Added back warning background for dangerous operations
Remove silly shadow
Indent lists
Fix indent for unordered lists as well
Merge pull request #2876 from davidegrohmann/2.2-fix-muninn-shutdown-races

Fix races on shutdown in Muninn
re-introduce border on code blocks