* helm: add support for history-max parameter
The --history-max parameter allows the user to set a maximum amount of
revisions per release to be kept in the history.
By default helm keeps 10 revisions per release, which means that 10
secrets will be kept per release.
* helm: remove default for history_max
When the history_max option is not set, the module will not pass
'--history-max' to the CLI command. This ensures that the defaults of
the helm CLI will alwasy be used.
* helm: remove whitespace trail
* helm: add mutually exclusive logic
The 'history_max' parameter is not available when using the 'helm
install' command, it is only implemented for 'helm ugprade'.
The 'replace' option uses the 'install' parameter, thus 'replace' and
'history_max' have to be mutually exclusive.
* helm: formatting changes
