Update keepStrings behavior to reflect changes in keepBooleanAsString, keepNumberAsString

[marilynel]

#967

[stleary]

What problem does this code solve?
Fixes an inconsistency in how keepStrings is handled. For example, if keepStrings was set, the keepStrings flag was not set.
The new behavior is:

• If keepStrings is set, the keepStrings, keepBooleanAsString, and keepNumberAsString flags will be set accordingly.
• If either keepBooleanAsString or keepNumberAsString is set, then keepStrings will be set accordingly.
  Internally, there is no change to the existing behavior.

Does the code still compile with Java6?
Yes

Risks
Low

Changes to the API?
No

Will this require a new release?
No

Should the documentation be updated?
No

Does it break the unit tests?
No, new unit tests were added.

Was any code refactored in this commit?
No

Review status
APPROVED

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