wait for green/yellow status
Never throw an IAE if the IndexMapper isn't present in PostingsFormat

If we throw an exception in the PostingsFormat during a merge we essentially
fail the entire merge which can lead to a corrupt index. We should rather
return the default postings format for the new segment and log a warning.

Closes #3088
Fixing percolation of documents with TTL set

When a type is configured with a TTL, percolation of documents of this type
was not possible. This fix ignores the TTL for percolation instead of
throwing an exception that the document is already expired.

Closes #2975
Stabilized SimplePercolaterTests
Added sorting by child values. (Work in progress)
add nested support
Moved each field values collector to its own class.
renamed package
Updated to latest master