
RTD cannot install several requirements files (SIGH), not does it use pip to install projects (SIGH#2). This change creates a new requirement file doc/joined-requirements.txt and links to both doc/requirements.txt and root requirements.txt from it. Note that we cannot put -r instructions to doc/requirements.txt since it's managed by global-requirements. Change-Id: Iaebf5917dc20d063e506a055d9f5af4daee0415b