Added documentation for Continuous Mapping, and Cron based scheduling

[Prachi Garg]

Engineers,

Can someone please review the documentation for -

   - Continuous Mapping -
   http://apacheignite.gridgain.org/v1.5/docs/continuous-mapping
   - CRON based scheduling -
   http://apacheignite.gridgain.org/v1.5/docs/cron-based-scheduling

I will make it public and copy it to v1.6 after it is reviewed.


Thanks,
-Prachi