Testing: Improve instructions and process #8844

[tshradheya]

Fixes #8844

• Fixes IntelliJ cannot run failed tests #8740
• Fixes Tests: certain tests are locale-dependent #8557
• Fixes Firefox: version 46.0.1 causing styling issue #8763
• Fixes StudentProfileAttributesTest: fix instability due to modified timestamp comparison #8871

Ongoing.

@LiHaoTan Need your input on the Intellij use default reporter

Would appreciate if someone can try out the following for me and check if it works on Eclipse

1. Change the language of eclipse IDE to German.
2. Run `TimeHelperTest` and ensure it fails
3. Make the necessary changes in `gradle.properties` as made in this PR
4. After rebuilding run the same test again and ensure it passes.

Outline of Solution

• Made default reported being true so that its standardized for IntelliJ
• Ensured tests are not locale-dependent
• Corrected minor problem in documentation

NOTE: Continued from #8845 as I messed up the old PR :P