Changed license from GPL-3.0 to Apache-2.0

[rascaraficci]

From now on this service is licensed under Apache License, Version 2.0.

• Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  It changes the license.

• What is the current behavior? (You can also link to an open issue here)
  NA

• What is the new behavior (if this is a feature change)?
  NA

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  No

• Is there any issue related to this PR in other repository? (such as dojot/dojot)
  dojot - Studies for changing Software License to Apache 2.0 dojot#1879

• Other information:

[codecov]

Codecov Report

Merging #172 (e34f3d9) into development (4648526) will not change coverage.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           development     #172   +/-   ##
============================================
  Coverage        73.64%   73.64%           
============================================
  Files               17       17           
  Lines             1711     1711           
============================================
  Hits              1260     1260           
  Misses             451      451           

Impacted Files	Coverage Δ
DeviceManager/__init__.py	100.00% <100.00%> (ø)

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