docs on storage and consistency
fixup! docs on storage and consistency
Merge pull request #1409 from crate/dobe-consistency

docs on storage and consistency
update es/upstream to include UnicastZenPing change

nodes should accept pings while in disabled state.
fix locking in MergeOperation addRows
add RelationOutput symbol and ExpressionAnalyzer

This commit adds a RelationOutput, ExpressionAnalyzer and a
RelationOutputResolver.

The ExpressionAnalyzer can be used to convert Expression
(from SQL AST) into a Symbol. Using composition over
inheritance makes it possible to easier handle nested
relations and re-use the ExpressionAnalyzer for different
sources.

The DataStatementAnalyzer is now marked as deprecated and
shouldn't be used anymore.
use ExpressionAnalyzer in CopyStatementAnalyzer
change Delete Analysis to relation structure

DeleteAnalyzedStatement now has a relation as source/target
instead of tableInfo.

In case of bulk operations there are now longer nested full
blown AnalyzedStatements but only multiple WhereClauses.