Kill 2.x compilation from UI
Kill all code related to 2.x compilation

(Except for legacy memento deserializer, which will be useful for migration.)
LRFile → LRLegacyFile; kill unused Step
LRFile2 → LRProjectFile
WIP on moving to LRProjectFile-based API
Add - [LRProjectFile description]
Rearrange analysis code a bit
Rearrange Project.m code
Animate the icon while a build is running
Start sending reload requests again
LRTest → LRSelfTest
Disable LRLegacyCompilationTests
Add a browser reloading test
Add tests for the reloading cases broken by 2.x → 3.x transition
Don't send reload requests for compiled sources
Move compilation coordination into LRBuildResult
Merge consecutive changes into a single build
Send fake changes for compilable files which don't get compiled by LR
Merge branch 'feature/remove-2x-compilation' into develop