MXS-1346: Disallow convoluted rule names

The rule names could have punctuation in them which caused unnecessary
complexity. Keeping the identifiers simple makes it easier to process.

Documentation/Release-Notes/MaxScale-2.2.0-Release-Notes.md

@@ -89,6 +89,11 @@ The `function` type rule will now match a query that does not use a function
 when the filter is in whitelist mode (`action=allow`). This means that queries
 that don't use functions are allowed though in whitelist mode.
 
+#### Rule Names
+
+Rule names can no longer use punctuation in them and can consist only of
+alphanumeric characters, underscores and hyphens.
+
 ### Logging
 
 When known, the session id will be included in all logged messages. This allows

server/modules/filter/dbfwfilter/token.l

@@ -19,7 +19,7 @@
 %option reentrant noyywrap bison-bridge prefix="dbfw_yy"
 %option yylineno
 
-RULENAME    [-_[:alnum:][:punct:]]+
+RULENAME    [-_[:alnum:]]+
 STR         [_[:alnum:]]+
 TIME        [0-9]{2}:[0-9]{2}:[0-9]{2}-[0-9]{2}:[0-9]{2}:[0-9]{2}
 QSTR        (\"[^\"]*\")|('[^']*')
@@ -29,7 +29,6 @@ INT         [0-9]+
 FLOAT       [0-9]+[.][0-9]+
 SQL         select|insert|update|delete|grant|revoke|drop|create|alter|use|load
 PIPE        [|]
-USER        [^[:space:]]*[@]
 IP          [0-9]{1,3}[.][0-9]{1,3}[.][0-9]{1,3}[.][0-9]{1,3}
 BTSTR       `[^`]*`
 USTR        [%-_[:alnum:][:punct:]]+