Use beforeEach and afterEach instead of initialization code in describe blocks

[timvandermeij]

This might make the unit tests a bit slower (as we might, for example, read one file for each test instead of just once), but it is the recommended way to setup and tear down unit tests properly.

Blocked by #6877.

[Rob--W]

We're currently using Jasmine 1.1.0 (https://github.com/mozilla/pdf.js/tree/58329f7f92f9c9f5dd8a7e42caf6ba3afdd6911d/external/jasmine), which is over 4 years old. Meanwhile Jasmine has improved a lot (in particular in the syntax for asynchronous tests, using explicit callbacks instead of error-prone waitsFor calls), so upgrading to the latest version of Jasmine (and putting the dependency in package.json instead of external/jasmine) might make it easier to enhance the tests.

[yurydelendik]

Jasmine was updated to 2.4.1 by #7129

[yurydelendik]

There is also beforeAll and afterAll, see http://jasmine.github.io/2.4/introduction.html#section-Setup_and_Teardown

[yurydelendik]

TODO:

• crypto_spec: inside "CipherTransformFactory"
• dom_utils_spec: inside "isExternalLinkTargetSet"
• font_spec: inside 'font' (maybe), 'CFFParser',