Add wifi module logic

[platisd]

Description

This feature adds the initial Wifi module business logic. Particularly, the submitted code shall:

• Connect to the specified Wifi network.
• Figure out the MAC address - RSSI value pairs of the positioning wifi network (not necessarily the same).
• Transmit them (once) to the specified server and port number via a POST request.
• Deep sleep and notify power controller to turn it off in case of failure or once it has finished transmission.

Server output upon successful transmission (where I have two access points and obfuscated their MAC addresses):

[2017-12-03 14:21:47.993] [INS-Server] [debug] + IndoorNavigationService::SetReceivedSignalStrengths [2017-12-03 14:21:47.993] [INS-Server] [debug] + DataStore::CreateDeviceTable [2017-12-03 14:21:47.993] [INS-Server] [debug] CREATE TABLE IF NOT EXISTS dev_1(id INTEGER PRIMARY KEY,mac_addr TEXT, rssi REAL,timestamp datatime default current_timestamp); [2017-12-03 14:21:47.993] [INS-Server] [info] SQL executed successfully [2017-12-03 14:21:47.993] [INS-Server] [debug] - DataStore::CreateDeviceTable [2017-12-03 14:21:47.993] [INS-Server] [debug] + DataStore::InsertRSSIReadings [2017-12-03 14:21:47.993] [INS-Server] [debug] INSERT INTO dev_1 (mac_addr, rssi) VALUES('AA:AA:AA:AA:AA:5C',-73),('AA:AA:AA:AA:AA:F0',-64); [2017-12-03 14:21:48.097] [INS-Server] [info] SQL executed successfully [2017-12-03 14:21:48.097] [INS-Server] [debug] - DataStore::InsertRSSIReadings [2017-12-03 14:21:48.097] [INS-Server] [debug] - IndoorNavigationService::SetReceivedSignalStrengths

Solved issue(s)

Fixes #44

[codecov[bot]]

Codecov Report

Merging #64 into dev will increase coverage by 4.86%. The diff coverage is 100%.

@@            Coverage Diff             @@
##              dev      #64      +/-   ##
==========================================
+ Coverage   68.39%   73.25%   +4.86%     
==========================================
  Files           9       10       +1     
  Lines         367      430      +63     
==========================================
+ Hits          251      315      +64     
+ Misses        116      115       -1

Impacted Files	Coverage Δ
ins-node/src/wifi_module/wifi_credentials.h	100% <100%> (ø)
ins-node/src/wifi_module/wifi_module.ino	100% <100%> (+25%)	:arrow_up:

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