Add a way to set resource limits/requests on running pods

Ref: https://github.com/kubernetes/kubernetes/issues/21648

I squashed the commits to make rebasing easier
Change log:

- fixed a typo that caused the command to be run with kubectl set set instead of the correct kubectl set limit

- added a ResourcesWithPodTemplates to pkg/kubectl/cmd/util/factory.go
     instead of hardcoding these resources move there description all in one place

- Fixing some of the flow control in kubectl set limit

- update the help info

- changed the name of ResourcesWithPodTemplates to ResourcesWithPodSpecs to more accuratly describe what it is doing
    and changed the variable names to lower case to conform to go's variable naming convention

- changing the name of the command from 'set limit' to 'set resources'

- Adding the new file pkg/kubectl/cmd/set/set_resources.go

- changes to the test cases to reflect the change from 'kubectl set limit' to 'kubectl set resources'

- comment removed

- adding the man page to the git repository attempting to fix Jenkins tests

- adding the user guide

- fixed a few typos

- typo in hack/cmd-test.sh

- implamenting suggestions for command help text

- adding the dry-run flag

- removing the "remove" option in favor of zeroing out request/limits in order to remove them

- changed limits/requests to requests/limit

- changing ResourcesWithPodSpec

- updated generated docs and removed whitespace

- change priint on success message from "resource limits/requests updated" to "resource requirements updated"

- minor rebasing issues - 'hack/test-cmd.sh' now passes

- cmdutil.PrintSuccess added another argument

- fixing mungedocs failure

- removed whitespace from hack/make-rules/test-cmd.sh and an erroneous entry from pkg/cloudprovider/providers/openstack/MAINTAINERS.md

- fixed typo in Short: field of the cobra command

- rebased

- Creating a new factory in the ResourcesWithPodSpecs() so that the testing will pass

- changing ResourcesWithPodSpecs, it doesn't need to be a method of factory