Read module dependencies from meta.yml

[jvfe]

Current Scenario

• Currently, get_components_to_install is the function used to download and update both subworkflows and modules.
  

• It gets called as part of the init method of the ComponentInstall class, which is used for both modules and subworkflows.
  f

• The function itself only takes subworkflow_dir as an argument, and attemps to find the respective modules using relative paths.

Proposed solution

• Change the function to read from a subworkflow's meta.yml, which will contain extra keys when necessary, to specify if the module should be pulled from a different remote and not the one the subworkflow is hosted in.
• This idea was originally suggested here

[jvfe]

Done in #8