PostgreSQL: Add 9.4 Beta

- Require extra component (9.4) from PGDG apt repository
- PostGIS 2.1 not supported yet
PostgreSQL: fix a bug in init.d script

Without this change the return code of 'status' is wrong.
PostgreSQL: Add support for Trusty (Ubuntu 12.04)
PostgreSQL: Keep 12.04, only run on 14.04/12.04

- Reintroduce the platform support clause in default.rb
- Use postgis PPA when provisioning Precise (12.04)

Resolve conflicts from developing branch:
	ci_environment/postgresql/recipes/default.rb
	ci_environment/postgresql/recipes/postgis.rb
Merge pull request #402 from travis-ci/gc-patch-trusty

Patch for Trusty development branch