prepare release 0.43.0
added graceful_stop cluster settings
documentation for graceful_stop cluster settings
implemented rounting.allocation.enable setting
test fixup
changed implementation of global settings
added cluster upgrade settings to crate.yml
added docu for extended cluster settings
moved settings documentation from reference to documentation
added missing configuration settings description
to crate.yml
implemented mostly all dynamic cluster setting expressions
fixed setting object settings
added missing settings to documentation
added missing settings to crate.yml
validate every object element while applying whole object to setting
changed style of settings documentation,
documented runtime changeable settings
new snapshot version 0.44.0
hide graceful_stop cluster settings
Merge pull request #1159 from crate/set-minimum-master-nodes

Set minimum master nodes
fixed streaming of cluster settings
(stream TimeValue & ByteValue as strings)