* Refactor payloads.

* Payloads handlers (#325)

* Multiple payloads support

* RHost for bind shell

* Fixing payloads

* Validating parameters

* Architecture parameter

* Fixing payloads

* Fix pep

* Fixing tests

* Fixing ident

* Payload handlers

* Removing old payloads

* Removing default target/port

* Fixing payloads, refactoring

* Fixing pep

* Changing payloads names

* Adding wget and echo options

* Parameter validation

* Removing testing modules

* Refactor payload vol. 2

* Remove `ArchitectureHeader`.

* Put PayloadHandler mixins first in MRO.

* Add `ExploitOptionsAggregator` metaclass to mixins.

* Fix payload completion.

* Remove validate_template from shell()

* Fix tests.

* Fix flake8 violations.

* Adding validation

* Adding support for generic payloads

* Add meaningful error message.