Also adds Java API for doing the same to Java threads (standard Java Thread.setPriority only works
when Java is run as root, even if the process has the right privileges).
Subsections are alphabetized according to lexographic ordering. Also, HAL includes were moved from headers to source files where possible. This change may cause user code which uses HAL functionality and does not include the relevant HAL header (since it may have been provided by another WPILib header) to fail to compile.
Rename the following folders:
hal/lib/Athena -> hal/lib/athena
hal/lib/Desktop -> hal/lib/sim
hal/lib/Shared -> hal/lib/shared
wpilibc/Athena -> wpilibc/athena
wpilibc/simulation -> wpilibc/sim
Windows users may need to run gradlew clean after updating.
