FlatBuffers gradle setup

[collinsmith]

f361d48 added support for FlatBuffers, however the gradle config needs to be fixed, and there doesn't seem to be much support.

• Current build process assumes flatc is on the system's path -- should this be included within the repo? My instinct is yes to ensure flatc.exe is the same version as the gradle version
• createFlatBuffers task compiles schemas to java sources in gen/ -- should this be within build/generated and not included within repo? (this would mean that people trying to build the sources would need to compile the schemas to generate the java sources and then have those compiled to classes)
• gen/ is not automatically detected as Generated Sources Root by IntelliJ IDEA -- I configured this as one of the source sets because I want the compiler to compile these as well, however idea.module.generatedSourceDirs doesn't seem to be working unless I am misunderstanding

Anyways, I need to figure this stuff out. In the meantime, as I hash out the FlatBuffer schemas, I think I will include their generated java sources in the repo as needed until I can figure out the correct procedure.

[collinsmith]

I had to lower the version to 1.9.0 because I was getting a DexArchiveBuilderException when trying to build for android with 1.10.0. This will need to be looked into later if it's an issue on my end. May require a new issue because I'd like to use as new as possible.

[collinsmith]

This issue is old and the info is outdated. Flatbuffers project dependency is currently on 1.11.0. See #132