Sketch a PathFilter that uses the regex machinery to handle globbing.
Sketch a PathFilter that uses the regex machinery to handle globbing.

* Add case-sensitive trigram fields for path.
* Add es_regex_filter(), which we can use for full regex queries too.
* Add a PathFilter whose callees aren't done yet and which needs highlighting but is complete enough to show what lower-level things we need to build.
pelmers/dxr,kleintom/dxr,gartung/dxr,pombredanne/dxr,gartung/dxr,jbradberry/dxr,pombredanne/dxr,pelmers/dxr,bozzmob/dxr,bozzmob/dxr,bozzmob/dxr,pombredanne/dxr,pombredanne/dxr,kleintom/dxr,bozzmob/dxr,jay-z007/dxr,gartung/dxr,gartung/dxr,gartung/dxr,jay-z007/dxr,jbradberry/dxr,pelmers/dxr,jbradberry/dxr,pombredanne/dxr,jay-z007/dxr,jbradberry/dxr,jay-z007/dxr,pombredanne/dxr,kleintom/dxr,jbradberry/dxr,pelmers/dxr,kleintom/dxr,jay-z007/dxr,pelmers/dxr,kleintom/dxr,jbradberry/dxr,bozzmob/dxr,jbradberry/dxr,pelmers/dxr,pelmers/dxr,jay-z007/dxr,pombredanne/dxr,kleintom/dxr,kleintom/dxr,gartung/dxr,jay-z007/dxr,bozzmob/dxr,gartung/dxr,bozzmob/dxr