Build library system

The dev.jeka.core.api.system package provides system level functions :

• JkInfo Provides meta information as the running version of Jeka.

• JkLocator Provides information about where the repository cache or Jeka user home are located.

• JkLog Provides API to log Jeka event. It supports hierarchical logs through the #startTask and #endtask methods.

• JkProcess Launcher for external process.

• JkPrompt One-liner to ask for user input.