Move the 'meta' dir to 'lib/cretonne/meta'.

The 'lib/cretonne' directory will be the new root of a stand-alone
cretonne crate containg both Python and Rust sources.

This is in preparation for publishing crates on crates.io.

docs/conf.py

@@ -24,7 +24,7 @@ sys.path.insert(0, os.path.abspath('.'))
 
 # Also add the meta directory to sys.path so autodoc can find the Cretonne meta
 # language definitions.
-sys.path.insert(0, os.path.abspath('../meta'))
+sys.path.insert(0, os.path.abspath('../lib/cretonne/meta'))
 
 # -- General configuration ------------------------------------------------