Component hot deployment

Hot deployment of new/upgraded components is a critical requirement in many scenarios. A few suggestions are :

1. Hot deployment of new processors/components
2. Hot deployment of processors/components that are not used in current flow context
3. Rolling upgrades (in a cluster)

"Hot deployment of new processors" has immediate benefits. For example it helps in two very common scenarios :

a) Development of a complex processor that uses a few nifi services (where mock framework only helps partially). (might be simple in a single node!) .
b) Complex system that can't be restarted (Or has very short maintenance time : a few hours each month/year). In this situation we could build "upgraded processor" and use them as "new processor".