Allow filtering to a date range

[jyasskin]

Especially useful if I'm looking for documents on a project that started in the last year or two.

[salamanders]

good FR. I'm considering a hard 2 year limit because it would be a fast patch.

[gurayAlsac]

Are there any limits currently? Or limitations/restrictions on the drive apis that impose an effective limit?

[salamanders]

I tossed in a 2 year ago limit. But no, no API limit that I'm aware of.

AND viewedByMeTime>='${oldestDateString}' AND modifiedTime>='${oldestDateString}'

[salamanders]

Closing because people seem ok with the 2 year range. Open to a pull request for a more dynamic solution.