brjs command global install

[leggetter]

Make brjs a globally installed command, where the apps and sdk live independently of each other.

To achieve this I'm assuming that the CLI commands may also need to be context-aware (#885) e.g. run brjs create-blade from within an application directory to create a Blade for an app

• - context aware commands - make commands 'context' (directory) aware #885 [deprioritised]
• - change BRJS.initialize so it no longer scans upwards to find the BRJS dir - update BRJS.initialize() to simply use the directory given #95
• - update the BRJS.initialize() method to take two directories instead of one in preparation for making BladeRunnerJS a global command - see update the BRJS.initialize() method to take two directories instead of one in preparation for making BladeRunnerJS a global command #93
• - Allow BRJS to be run from outside of the SDK directory by putting brjs on the PATH - Allow BRJS to be run from outside of the SDK directory by putting brjs on the PATH #1130
• - allow apps to live seperately from the sdk - allows apps to live separately from the SDK #1154

[dchambers]

I think the global-install feature is a misnomer, as global-install is actually undesirable while BRJS includes Javascript libraries that an app depends on, and which should either be checked in together with the app, or which should be part of a manifest so that the correct versions can be downloaded on the developer's machine.

Instead, here is my current guess as to the desirable features of this story:

• It should be possible to install multiple versions of BRJS on a single machine.
• For convenience, it should be possible to configure the path to point the default BRJS installation on a machine.
• It should be possible to run BRJS commands relative to app directories.
• There should be no requirement that all apps reside within a single 'apps' directory.
• It should be possible to check BRJS in to version control, along with any apps that depend on it.

[andy-berry-dev]

Apart from #885 which has been deprioritised, this has been completed and it's now possible to run brjs from the PATH and keep apps seperate from the SDK itself.