Introduce BytesTransportRequest, allowing for downstream network optimization in buffers usage
When sending a request, mainly to multiple nodes, if we already have the "body" of the request in bytes, we can share it instead of copying it over to a new buffer. Also, it helps a lot when sending a relatively large body to multiple nodes, since it will use the same body buffer across all nodes
Add wildcard support to field resolving in the Get Field Mapping API

Closes #4367
Packaging: Ensure setting of sysctl vm.max_map_count

In order to be sure that memory mapped lucene directories are working
one can configure the kernel about how many memory mapped areas
a process may have. This setting ensure for the debian and redhat initscripts
as well as the systemd startup, that this setting is set high enough.

Closes #4397