backend: Add new ajax function.
backend: Add new ajax function.

  * Add new ajax function for bisecting.
  * Refactor how URL tokens are concatenated.

Change-Id: I82d089436e83843410aa52c63df0015737ee4e5d

kernelci/kernelci-frontend,kernelci/kernelci-frontend,kernelci/kernelci-frontend,kernelci/kernelci-frontend