TreePPL managment

[ThimotheeV]

New way to manage TreePPL self-container (tpplc).

Now a treeppl directory will be create next to treepplr directory (using .libPath()) . This treeppl will contain a associate version of the tpplc for the package version. This version is HARDCODED on the value TPPLC_VERSION present zzz.R (standard terminology ^^) .

Order of check :

• /tmp/
• .libPath()[1]/treppl/version
• https adress

Good points :

• Much more easier to manage.
• Less download in a dev context.
• Vignette and Check Compatible (only one dwl if tpplc not in /tmp).

Bad point :

• Haven't been test on Mac Environment.
• Need to manually change TPPLC_VERSION each time we want to update to the new release.
• Unique association between the version of the package and the version of TreePPL self-container.
• Will break if we change the nomenclature or the way we distribute TreePPL self-container .

Base on stenio work (fork commited)