Support some launch jar manifest keys

[Gaming32]

The idea is to add support for reading (and acting upon) the Add-Exports, Add-Opens, and, in the future, Enable-Native-Access manifest keys. This would allow mods to apply workarounds to the JDK similar to how SecureJarHandler does. It would also allow mods to use Project Panama for native access.

[shartte]

Yeah we have that under consideration for the future, the format of how this is applied is unclear yet, and it needs further infrastructure that currently does not exist.