handle multiple versions

[petejkim]

• activate version on install
• start/stop/status/restart should control current active version
• parts list

mongodb (2.4.6)
php5 (5.5.8-nitrous2)
apache2 (2.4.6, 2.4.7*)

* indicates selected version

• parts which - list selected versions

mongodb 2.4.6
php5 5.5.8-nitrous2
apache2 2.4.7

• parts which apache2

apache2 2.4.7

• parts switch apache2 2.4.6 - activate older version for use
• parts uninstall apache2 --version 2.4.6
• parts purge apache2 --version 2.4.6
• parts upgrade - upgrade all outdated installations
• parts cleanup - remove all unselected old versions

[petejkim]

wip

[petejkim]

putting this on hold for now, there are other problems with supporting multiple versions like /etc/*.conf files being incompatible between versions...