New roles and some cleanup of postgres role

New roles for
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1. Installation of chrome browser, Virtualbox (from appropriate repositories)
2. Installation of Oracle java using locally downloaded tar.gz file containing jdk 
3. Hook into alternatives system (used by oracle java installation) 
4. Role for uploading sudoers file (that also checks it's format before changing the sudo file)
5. Role for installing motd
6. Versioned role --- that enables one to have evolving setup of target servers, probably makes no sense for webserwer, but for one of my usages it is important. 

Changed roles 
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1. Rewrote most part of BasePostgres role, so it uses only psql command and psql scripts. At some point I'll rewrite rest of it, so for example ensure_user will execute single psql command. 
2. Added some stuff to base.Role, like creating temp files with random names. 
3. Added context manager for Aptitude role that temporalily disables provisioning for aptitude role.