Add wildcard and prefix intervals

[romseygeek]

We should expose the wildcard and prefix IntervalSource implementations
as providers in elasticsearch.

{ "prefix" : {
    "term" : term prefix,
    "analyzer" : optional analyzer (uses normalize() function),
    "use_field" : optional field switch
}}
{ "wildcard" : {
    "term" : term glob,
    "analyzer" : optional analyzer (uses normalize() function),
    "use_field" : optional field switch
}}

Span queries also allow you to wrap regexp and term range queries, and we can
consider adding these here as well, although they will also require some work in
lucene.

The prefix source can piggy-back on text fields index_prefixes functionality to
rewrite to simple term intervals sources

[elasticmachine]

Pinging @elastic/es-search