Add date interval as searching parameter

[davidmarcos98]

fixes #128

Adds new Searching parameter to allow filtering maps inside a date interval. This is useful to be able to play maps only before an important game patch or update, for example. This setting is only used if CustomRules setting is also set to true, to prevent these runs getting into the official leaderboard.

Date parsing from a string is done using this suggestion by @misfitmaid