Import utilities to create device factories from almond-cloud

[gcampax]

This is code that has been copied to almond-cmdline and almond-server
to implement "developer mode", and it's best if shared. Also,
this simplifies adding new kinds of loaders or config modules,
cause almond-cloud no longer needs to change.

[gcampax]

Btw, I don't quite like the name DeviceFactoryUtils, because it overlaps with DeviceFactory (which is a different thing). I'm open to suggestions of a better name before this becomes API we have to maintain until Tp 3.0

[coveralls]

Pull Request Test Coverage Report for Build 217

• 45 of 55 (81.82%) changed or added relevant lines in 2 files are covered.
• 43 unchanged lines in 11 files lost coverage.
• Overall coverage decreased (-0.2%) to 83.81%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/device_factory_utils.js	43	53	81.13%

Files with Coverage Reduction	New Missed Lines	%
lib/base_client.js	1	85.71%
lib/base_device.js	1	95.65%
lib/helpers/polling.js	1	95.0%
lib/base_engine.js	2	80.0%
lib/helpers/ref_counted.js	2	86.27%
lib/utils.js	2	91.09%
lib/helpers/file_prefs.js	5	77.78%
lib/factory.js	6	62.5%
lib/helpers/object_set.js	6	84.62%
lib/http_client.js	8	78.26%

Totals
Change from base Build 207:	-0.2%
Covered Lines:	1203
Relevant Lines:	1380

---

💛 - Coveralls

[sileix]

Maybe call it DeviceCofigUtils?