Fixed libcrypto in docker images, added C++ support

Fixed libcrypto in docker containers, misc C++ fixes (#11)

* Fixed how libcrypto and cmake are applied to images

* Make sure packages/compiler_packages can be per-package tool

* Added support for --branch argument to specify a specific branch

* Fix to allow projects to empty out build/test steps

* Use path to compiler for C/C++ when telling cmake

* Re-enabled c++ compiler installation by default

* Fixed package names for gcc packages