better logic on sending mapping update new type introduction

when an indexing request introduces a new mapping, today we rely on the parsing logic to mark it as modified on the "first" parsing phase. This can cause sending of mapping updates to master even when the mapping has been introduced in the create index/put mapping case, and can cause sending mapping updates without needing to.
 This bubbled up in the disabled field data format test, where we explicitly define mappings to not have the update mapping behaviour happening, yet it still happens because of the current logic, and because in our test we delay the introduction of any mapping updates randomly, it can get in and override updated ones.
Can you add quick documentation of what the boolean in the tuple means?