Replace assertTrue and assertFalse with more suitable asserts

The following replacements were done to have
clearer messages in case of tests failure:
- assertTrue(* in *) with assertIn
- assertFalse(* in *) with assertNotIn

Change-Id: I7cc2ed4365895c430220798de14dc6c5d599e7bd
Fix spelling mistakes in docs

Noticed a bunch of minor spelling mistakes.

Change-Id: I8189dda5a78418820e6c56270089590ef87f1495
Closes-Bug: #1323361
Merge "Fix spelling mistakes in docs"
Merge "Replace assertTrue and assertFalse with more suitable asserts"