Allow {} to be used for quoting in query expressions

This makes it a little easier to query for group names that contain
a space over SSH:

  ssh srv gerrit query " 'status:open NOT reviewerin:{Developer Group}' "

Change-Id: I7c81c752236c85d4ed5bd3ed7ad79486b3336510

Documentation/cmd-query.txt

@@ -37,10 +37,14 @@ results beyond the limit, the 'resume_sortkey:' operator can be used
 to resume the query at the change that follows the last change of
 the prior result set.
 
-Non-option arguments to this command are joined with spaces and then
+Non-option arguments to this command are joined with spaces and
-parsed as a query.  This simplifies calling conventions over SSH
+then parsed as a query. This simplifies calling conventions over
-by permitting operators to appear in different arguments without
+SSH by permitting operators to appear in different arguments.
-multiple levels of quoting required.
+
+Query operators may quote values using matched curly braches
+(e.g. `reviewerin:{Developer Group}`) to sidestep issues with 2
+levels of shell quoting (caller shell invoking SSH, and the SSH
+command line parser in the server).
 
 OPTIONS
 -------

Documentation/user-search.txt

@@ -23,6 +23,7 @@ matches the search, the change will be presented instead of a list.
 |Open changes in Foo  | status:open project:Foo
 |=================================================
 
+
 Basic Change Search
 -------------------
 
@@ -109,7 +110,6 @@ matches project names by regular expression.  The
 link:http://www.brics.dk/automaton/[dk.brics.automaton
 library] is used for evaluation of such patterns.
 
-
 [[branch]]
 branch:'BRANCH'::
 +
@@ -271,6 +271,17 @@ status:abandoned::
 Change has been abandoned.
 
 
+Argument Quoting
+----------------
+
+Operator values that are not bare words (roughly A-Z, a-z, 0-9, @,
+hypen, dot and underscore) must be quoted for the query parser.
+
+Quoting is accepted as either double quotes
+(e.g.  `message:"the value"`) or as matched
+curly braces (e.g. `message:{the value}`).
+
+
 Boolean Operators
 -----------------
 
@@ -427,6 +438,7 @@ set by the pagination system as the user navigates through results
 of a query.  Including either value in a web query may lead to
 unpredictable results.
 
+
 GERRIT
 ------
 Part of link:index.html[Gerrit Code Review]

gerrit-antlr/src/main/antlr3/com/google/gerrit/server/query/Query.g

@@ -155,6 +155,10 @@ EXACT_PHRASE
       String s = $text;
       setText(s.substring(1, s.length() - 1));
     }
+  | '{' ( ~('{'|'}') )* '}' {
+      String s = $text;
+      setText(s.substring(1, s.length() - 1));
+    }
   ;
 
 SINGLE_WORD