lab.antlr.org is not displaying the start symbol correctly for javadoc

[kaby76]

• Select "javadoc" in the grammar drop-down.
• The lexer and parser grammars are correct, but the start symbol is wrong.
• grammars.json contains the correct entry for "start".
• There is an issue in the python indexer for the grammar: the files under subdirectory examples/javadoc are not listed.