[WIP] Added Javascript unit tests

- added Jasmine library
- added Sinon library (for stubs/mocks)
- added test.php in root to run app tests
- added a few unit tests for core and files

To run the core tests open `test.php` in a browser.
To run the files tests open `test.php?app=files` in a browser.

### Notes about this PR
- Not convinced yet about the main `test.php` to run JS tests. Another alternative is to have a test run from "index.php/apps/files/tests.php"
- Maybe need to replace the test templates in apps with a JSON file containing all scripts to be loaded including the test specs (JS files)
- Goal is to be able to run all test suites in one go (core + files + other core apps), or one test suite individually
- This is currently a minimal solution so we can at l(e)ast have unit tests for our JS code !

Please have a look @DeepDiver1975 @karlitschek @schiesbn