Show gutter icon for changed access when viewing an AT'ed dependency

[gabizou]

ForgeGradle 3 introduces better dependency management/generation for mappings and AT's to where a dependency that is obfuscated (vanilla) or SRG mapped (mods) can be access transformed, decompiled, renamed with MCP mappings, and then recompiled for verification, all during Gradle's dependency resolution step takes place.

One thing I've considered is that it would be possible to use the AT cache from FG to gutter iconize fields/methods/classes as being transformed for access. It's a wishful thinking sort of feature, but I believe doable nonetheless, especially since this can affect inter-mod dependencies.