prep for v0.0.18 release, brought in line with current project practice

Added go1.16 support, updated version and copyright year, adding M1 c…

…ompile support

renamed Verb.AddParams() to Verb.SetParams() to match Cli method name

bumped version number with merging of pkgassets as sub-package

bumped version number, renamed GenerateMarkdownDocs() to GenerateMark…

…down()

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