Update packages to version

[bosley]

Update how packages work so we can have multiple versions installed. Each package should have a "preferred version" that will exist in the package's directory in a config.saur

sauros_home
|
|--pkgs
       |
         \ net
             |-- config.saur
             |
             | v1.0.0/
             | v1.1.9/

The use command should take an extra optional string to specify the version to be used for the application:

[use "net" "v1.0.0"]

if The version doesn't exist, then we throw. 

[bosley]

This task entails updating the currently used packages to conform to this standard