Add `Dates.dateBasedDelta` and related methods.

No unit tests yet.
Let's try `date.jump( Day, -1 )`

We can get rid of all the `deltaDay`, `deltaWeek` etc methods now.

Debatable whether it's worth getting rid of `nextDay()` etc also.
Missing semicolon.
Merge remote-tracking branch 'origin/master' into feature/jump
replaced loops with divisions where possible
trying to make tests pass
renamed step methods
added tests for Dates.create
added Dates.create/Timestamps.create
refactored implementation of jump based on Dates.create()
changed implementation in snap methods
fixed C# issue with Arrays.compact
fixed platform specific issues
Merge pull request #33 from fponticelli/feature/jump

Feature/jump