Add support for implicit grant

[DeepDiver1975]

Fixes #165

Test Steps

0. add a new client using the occ command

 ./occ oauth2:add-client test clientid-1234567890-1234567890-1234567890 secret-secret-secret-secret-secret http://localhost:9999

1. open browser
   http://own.cloud.local/index.php/apps/oauth2/authorize?response_type=token&client_id=clientid-1234567890-1234567890-1234567890&redirect_uri=http://localhost:9999

2. See authorization dialog - click button 'Authorize'

3. See login dialog - login

4. See redirect to url http://localhost:9999/?access_token=BBtaHzdCpXoRnN912G7hCPVcSHLSpKZbVF5tuwaLgxajj3mbpik7m2MHJOty1Vxk&expires_in=3600

5. this access_token can now be used to call e.g.

curl -v http://own.cloud.local/index.php/apps/oauth2/api/v1/arer BBtaHzdCpXoRnN912G7hCPVcSHLSpKZbVF5tuwaLgxajj3mbpik7m2MHJOty1Vxk'

[codecov]

Codecov Report

Merging #166 into master will decrease coverage by 2.42%.
The diff coverage is 33.33%.

@@             Coverage Diff              @@
##             master     #166      +/-   ##
============================================
- Coverage      82.2%   79.77%   -2.43%     
- Complexity      200      204       +4     
============================================
  Files            21       21              
  Lines           708      727      +19     
============================================
- Hits            582      580       -2     
- Misses          126      147      +21

Impacted Files	Coverage Δ	Complexity Δ
lib/AuthModule.php	88.88% <100%> (ø)	8 <0> (ø)	⬇️
lib/Controller/PageController.php	48.14% <31.25%> (-7.89%)	38 <0> (+4)
lib/Db/Client.php	84.61% <0%> (-15.39%)	4% <0%> (ø)

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[PVince81]

Code looks good and seems to match what I read in https://alexbilbie.com/guide-to-oauth-2-grants/ 👍

@DeepDiver1975 can you add the test scenario that describes how to manually test this ?

[PVince81]

restarted CI for our favorite database...

[DeepDiver1975]

Oracle in travis is broken. There is another pr to move to drone

[karakayasemi]

@DeepDiver1975 I got the same error for oracle in the following PR. Fixed it by updating ubuntu repos. https://github.com/owncloud/brute_force_protection/pull/40/files#diff-354f30a63fb0907d4ad57269548329e3R24