xbee: experimental support for any coordinator

[Shulyaka]

This PR removes the dependency on coordinator-specific remote_at_command() by emulating it for other coordinators.

While this should work in theory with other coordinators, I could only test the code with xbee coordinator for the lack of hardware, I simulated it by slightly modifying zigpy_xbee code for the test.

[coveralls]

Pull Request Test Coverage Report for Build 1368197253

• 31 of 86 (36.05%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.7%) to 79.981%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
zhaquirks/xbee/init.py	31	86	36.05%

Totals
Change from base Build 1367560763:	-0.7%
Covered Lines:	4291
Relevant Lines:	5365

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💛 - Coveralls

[codecov-commenter]

Codecov Report

Merging #1089 (243ce09) into dev (2d5d68c) will decrease coverage by 0.70%.
The diff coverage is 36.04%.

@@            Coverage Diff             @@
##              dev    #1089      +/-   ##
==========================================
- Coverage   80.68%   79.98%   -0.71%     
==========================================
  Files         197      197              
  Lines        5280     5365      +85     
==========================================
+ Hits         4260     4291      +31     
- Misses       1020     1074      +54     

Impacted Files	Coverage Δ
zhaquirks/xbee/__init__.py	41.11% <36.04%> (-1.96%)	⬇️

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[Adminiuga]

did you sniff XBee commands and translated them into zigbee ZCL commands?

[Shulyaka]

Yes

[Adminiuga]

This is pretty cool. How can I test assuming I have a Xbee 2C or maybe xbee 3 joined as a router?

[Shulyaka]

What is your coordinator?

[Adminiuga]

EZSP based

[Shulyaka]

Great! If you have it already as a router, then you probably have switches for digital i/o. Just try to flip those switches and see if you get any exception. Flipping a switch generates an AT command that configures the pin. You can also double check the pin state with XCTU,