Bad behavior when parsing through shared / local symbol tables with at least 2 'symbols' / 'imports' / etc fields

[almann]

This looks like a bug within UnifiedSymbolTable and SharedSymbolTable classes. It looks like when parsing through either shared / local symbol tables, if there's more than one 'symbols' / 'imports' / etc field, they will be merged together.

For example, a local symbol table:

$ion_symbol_table::
{
  imports:[ { name: "symtab",
              version: 1,
              max_id: 75 }
  ],
  symbols:[ "rock", "paper", "scissors" ],
  symbols:[ "amazon", "dot", "com" ],
}

There are two 'symbols' field, and the UnifiedSymbolTable implementation will read in 6 local symbols.

We should write test files in IonTests to include coverage for other Ion libraries. We also need to clarify the appropriate behavior when this occurs on the specification documents.

Imported from ION-386,IONJAVA-34