Rename getProfiles to getProfileIds and add a proper getProfiles method

[scottinet]

Description

• User.getProfiles is renamed to User.getProfileIds
• User.getProfileIds now returns an empty array instead of undefined if no profile is attached to the user object
• add a new User.getProfiles method fetching profiles from Kuzzle API and returning an array of Profile objects

Boyscout

Update README file

Related issue

https://github.com/kuzzleio/kuzzle-sdk/issues/33

[codecov-io]

Codecov Report

Merging #225 into 5.x will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              5.x     #225      +/-   ##
==========================================
+ Coverage   98.15%   98.17%   +0.01%     
==========================================
  Files          17       17              
  Lines        1953     1971      +18     
  Branches      556      562       +6     
==========================================
+ Hits         1917     1935      +18     
  Misses         36       36

Impacted Files	Coverage Δ
src/security/User.js	98.76% <100%> (+0.35%)	⬆️

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