Add a powerful search engine based on lucene to the scm-manager api.
The api can be used to index objects, simply by annotating them and add them to an index.
The first indexed object is the repository which could queried by quick search in the header.
Add metrics about logging, file descriptors, process threads and process memory.
Rename scm.http.requests to http.server.requests to match micrometer defaults.
With this change the exposed metrics are now compatible (except for the tomcat metrics) to the official micrometer grafana dashboard (https://grafana.com/grafana/dashboards/4701).
Updates legman to version 2, which allows the usage of the MicrometerPlugin. The plugin will collect metrics for subscriber invocations and the underlying executor.
Furthermore this change will fix the usage of wrong subject context in the asynchronous events.
