[3793] Changes after review:
- {ptime,duration}ToText moved to lib/util - missing comments added - EXPECT_EQ -> ASSERT_EQ - several consts added - protected methods are now private in Observation - tabs converted to spaces
- {ptime,duration}ToText moved to lib/util - missing comments added - EXPECT_EQ -> ASSERT_EQ - several consts added - protected methods are now private in Observation - tabs converted to spaces