Allow users to set a limit on acceptable staleness

It should be possible for a user or operator to set a limit on how stale a member might be before allowing queries. An extension of this would be to improve driver discovery such that they do not choose a node that is excessively stale, when serving reads.

Exception messages for invalid maxStalenessMS values in ReadPreference constructor:

• "Expected maxStalenessMS to be >= 0, %d given", value
• "Expected maxStalenessMS to be <= %d, %d given", INT32_MAX, value
• "maxStalenessMS may not be used with primary mode"

Exception messages for invalid maxStalenessMS values in URI option parsing:

• "Expected maxStalenessMS to be >= 0, %d given", value
• "Expected maxStalenessMS to be <= %d, %d given", INT32_MAX, value
• "Primary read preference mode conflicts with maxStalenessMS"