documentation

Pull request #2085: Expression macros now support {FUNCTION.VALUE}

Merge in WEB/documentation from feature/ZBXNEXT-9229-7.2-D to release/7.2

* commit 'a14eb53841a24e116dba8aa6f8f5f0bf53ef537e':
  added that {FUNCTION.RECOVERY.VALUE} is supported in the event names; fixed a typo (ZBXNEXT-9229)
  {FUNCTION.VALUE} better description (ZBXNEXT-9229)
  Expression macros now support {FUNCTION.VALUE}