Fixes to HTTP code on "Using Data Types" page

Using -XPUT in the curl request examples for counters returned `405 Method Not Allowed`. Changing the three examples using -XPUT to use -XPOST instead allows the curl commands to function properly.

There are also two other curl examples that failed:
  • The example demonstrating that registers can also be removed contained an extra "update" bracket resulting in the error: `Invalid map field name 'remove'`.
  • The example demonstrating a map within a map within a map was missing a necessary "update" bracket resulting in the error: `Invalid operation on datatype 'map': "first_purchase_flag"`.