Allow stats retrieval for longer periods

[bennettmcelwee]

For example, summary for last 2 months, last 6 months, all time.

Also individual searches: last 1000, 10000; last month, all time.

[bennettmcelwee]

Prompted by https://wordpress.org/support/topic/log-lenght/ and others

[bennettmcelwee]

Use a filter to be able to customise values.
Summary always includes "yesterday & today". By default it also includes [7, 30], but you could set [7, 30, 60, 180]. Maybe allow 0 to mean all time.
Individual searches would default to [100, 500] but could set it to [1000, 10000]. Maybe also allow 0 and also "1m" for 1 month etc. Would complicate things a bit though.