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
Dates accessed from scripts should use UTC timezone
this was broken in the field data refactoring we did in 0.90, fixes #3091
Added indices aliases exists api.

Added indices aliases exists api that allows to check to existence of an index alias. This api redirects to the master to check for the existence of one or multiple index aliases.

Possible options:
* `index` - The index name to check index aliases for. Partially names are supported via wildcards, also multiple index names can be specified separated with a comma. Also the alias name for an index can be used.
* `alias` - The name of alias to check the existence for. Like the index option, this option supports wildcards and the option the specify multiple alias names separated by a comma. This is a required option.
* `ignore_indices` - What to do is an specified index name doesn't exist. If set to `missing` then those indices are ignored.

The rest head endpoint is: `/{index}/_alias/{alias}`

Examples:
Check existence for any aliases with the name 2013 in any index:
```
curl -XHEAD 'localhost:9200/_alias/2013
```
Check existence for any aliases that start with 2013_01 in any index
```
curl -XHEAD 'localhost:9200/_alias/2013_01*
```
Check existence for any aliases in the users index.
```
curl -XHEAD 'localhost:9200/users/_alias/*
```

Closes #3100
Make suggester implementation pluggable

This patch tries to make the suggester implementation as pluggable as
facets or highlight implementations. The goal is to be able to create
own suggest implementations in a suggest query.

Closes #3089
Reuse TestCluster in the background across tests running in the same JVM

TODO More info