documentation

[ZBXNEXT-2043,ZBXNEXT-2012,ZBXNEXT-2591,ZBXNEXT-5341,ZBXNEXT-2302] updated vmware documentation

* commit 'fa061c43e96e1497aed45ae71d852d93f9acfaeb':
  [ZBXNEXT-2578] renamed json fields
  discovery_fields.md minor correction
  added possible values to several items
  updated list of discovery fields (ZBXNEXT-2043, ZBXNEXT-4198)
  fixed spelling mistakes
  [ZBXNEXT-2043] aded few more details to vmware_keys.md
  [ZBXNEXT-2043] organised 'what's new' description
  [ZBXNEXT-7029] added discovery fields for vmware.dvswitch.discovery
  New fields for vmware.hv.net.if.discovery and better *.linkspeed description (ZBXNEXT-5431, ZBXNEXT-2043)
  [ZBXNEXT-2043] Adding VM snapshot metrics
  [ZBX-2012] additional NIC counters
  updated what's new for better redability
  [ZBXNEXT-2302] added new VM discovery field
  [ZBXNEXT-6517] vmware.vm.discovery returns info about resource pulls
  [ZBXNEXT-5341] added vmware.vm.attribute item
  [ZBXNEXT-2302] new vmware.* items (VMware Tools)