Add EnterAndHoldCriterion

[nimo23]

Fixes #.

Changes proposed in this pull request:

• EnterAndHoldReturnCriterion replaced by EnterAndHoldCriterion to calculate the "enter and hold"-strategy of any criteria.

• simplified VersusEnterAndHoldCriterion due to the use of EnterAndHoldCriterion

• Added a check in EnterAndHoldCriterion and VersusEnterAndHoldCriterion: If a BarSeries is empty, then 1 is returned

• added an entry with related ticket number(s) to the unreleased section of CHANGES.md

[nimo23]

@team172011 Please check:

• Added a check in EnterAndHoldCriterion and VersusEnterAndHoldCriterion: If a BarSeries is empty, then 0 is returned

Or should I return 1 instead of 0 when BarSeries is empty (as you did in #1095? If yes, then what does an EnterAndHold (or a VersusEnterAndHold) of "1" (100%) mean?

[team172011]

what does an EnterAndHold (or a VersusEnterAndHold) of "1" (100%) mean?

It means that you have neither profit nor loss, so you still hold 100 % of your invested amount of money. So 1 would be the correct value for empty bar series, because you will not be able to invest your money and neither face any profits nor face any losses

[nimo23]

So 1 would be the correct value for empty bar series, because you will not be able to invest your money and neither face any profits nor face any losses

OK, that makes sense. I also improved the javadoc.

@team172011 Perhaps you can also check any other criteria where this should be changed (i.e. if (barSeries == null) return series.one());)