Move stuff around to prep for future crates

Eventually, I want to take the code for working with the official binary
formats and split it out into a standalone library. The code for parsing
my unofficial text formats would then use that library as a dependency.

I might also spin off the text format code into its own library someday.
It might be useful to have a common text format.

This commit is just anticipatory prep work; I'm definitely not ready to
split this into a bunch of different crates today! I want to firm up the
data structures and the text format first.

src/zzt/error.rs

@@ -21,23 +21,17 @@ pub enum ParseError {
     #[error("board data too large")]
     BoardTooLarge,
 
-    #[error("parse error: {0}")]
-    ParseError(String),
-
-    #[error("text parse error: {message}")]
-    TextParseError { message: String },
-
-    #[error("invalid hex in terrain: {0}")]
-    InvalidHex(String),
+    #[error("nom error: {0}")]
+    NomError(String),
 }
 
 impl<I> NomParseError<I> for ParseError {
     fn from_error_kind(_input: I, kind: ErrorKind) -> Self {
-        Self::ParseError(kind.description().to_string())
+        Self::NomError(kind.description().to_string())
     }
 
     fn append(_input: I, kind: ErrorKind, other: Self) -> Self {
-        Self::ParseError(format!("{}: {:?}", other, kind))
+        Self::NomError(format!("{}: {:?}", other, kind))
     }
 }
 
@@ -45,7 +39,7 @@ impl From<nom::Err<ParseError>> for ParseError {
     fn from(value: nom::Err<ParseError>) -> Self {
         match value {
             nom::Err::Error(e) | nom::Err::Failure(e) => e,
-            nom::Err::Incomplete(needed) => Self::ParseError(format!("incomplete: {:?}", needed)),
+            nom::Err::Incomplete(needed) => Self::NomError(format!("incomplete: {:?}", needed)),
         }
     }
 }

src/zzt/mod.rs

@@ -2,9 +2,8 @@ mod elements;
 mod encoding;
 mod error;
 mod parse;
-mod text;
 
+pub use elements::{Element, element_id_from_name, element_name, resolve_alias};
 pub use encoding::{decode_multiline, decode_oneline, encode_multiline, encode_oneline};
 pub use error::ParseError;
 pub use parse::{Board, Program, Stat, Tile, World};
-pub use text::{board_to_text, text_to_board, text_to_world, world_to_text};