Begin making canonical variables explicit in AST

Also start migrating AST to the AST/ directory
Get rid of unused file
Migrate all of SourceSyntax/ to AST/
Get rid of old SourceSyntax files
Update Parse/ module for new AST structure
Add distinction for built-in values
Get rid of duplicate type alias for RawPattern
Tweak CanonicalBody and uncomment some Pretty code
Make listings sortable
Move RawType and CanonicalType into AST.Type
Handle BuiltIn properly
Starting to get Canonicalize working with new AST

canonicalize everything, even ports. Should set up to handle type alias
on ports.
Update JS generation code

Rely on new Canonicalization to get safe names. Get rid of SafeNames
module.
SourceSyntax/ => AST/ and get rid of dead files
SourceSyntax/ => AST/ in more modules

partial fix, still not in working order yet
Ignore build artifacts
Update sub-projects
Merge branch 'master' into canonicalize

Conflicts:
	Elm.cabal
Get rid of server code
Merge branch 'webgl' into canonicalize

Conflicts:
	Elm.cabal