Better behaved printing behavior

[cjvanlissa]

Many MplusAutomation functions print to the console using a combination of message() and cat(). This causes undesirable behavior when using MplusAutomation in RMarkdown files; it is exceedingly difficult to mute all these messages to get a clean, uncluttered manuscript. Recommend an overhaul of all functions to avoid unnecessary printing to console. Instead, objects should have print. methods.

[JWiley]

Note for anyone check, this is partially addressed in v1.0.0 by use of a quiet argument thanks to @cjvanlissa but I'm leaving open as the suggestion to avoid printing and implement print methods is a good one that is not yet done.