Add problem classes for squelch warnings/errors

This PR adds problem classes in order to squelch warnings/errors.

Problem class

Each problem is classified one problem class. For example, the following problems belong to lib/version problem class.

A Satyrographos library has an empty version id.
A Satyrographos library has an invalid version id.

Each OPAM Lint error/warning is considered as problem class opam-file/lint/<opam-warning-no>. For example, an empty synopsis field causes opam-file/lint/47.

`-W` option

-W option is added to disable warnings/errors being reported by lint subcommand. For example,

# Disable OPAM Lint Warnings 47, 48, and 50; and library version warnings
satyrographos lint -W 'opam-file/lint/{-47..50,+49},lib/version'

For now, -W option can disable not only warning but also errors. This behavior should be revised when lint subcommand is stable enough since errors should not be turned off.

-W option takes a warning expression. The grammar is following.

main ::=
  | exprs

exprs ::=
  | expr ( "," expr )*
    -- List of exprs
  | ( atom "/" )* "{" exprs "}"
    -- Common prefix for the exprs

expr ::=
  | ( "+" | "-" ) glob
    -- Enable or disable warnings matching the glob

glob ::=
  | "*"
  | atom
  | atom "/" glob
  | "{" globList "}"
    -- Alternative choose

globList ::=
  | glob
  | glob "," globList

atom ::=
  | id
  | range

id ::=
  | idCharFirst idChar

idCharFirst ::=
  | alphaNum

idChar ::=
  | idCharFirst
  | "_" | "-" | "."

range ::=
  | digit ".." digit

Examples:

+a/b enables warnings prefixed with a/b, e.g., a/b, a/b/c, but not a/bc or a.
+a/* enables warnings prefixed with a/, e.g., a/b, a/b/c, but not a/bc or a.
-*,+a disables all the warnings but ones prefixed with a.
a/{+b,-c} is equivalent to +a/b,-a/c
+a/{b,c} is equivalent to a/{+b,+c} so as to +a/b,+a/c.
+{1..3,a} is equivalent to +1,+2,+3,+a

This is the command line option for https://github.com/na4zagin3/satyrographos/issues/166

na4zagin3 / satyrographos