Added DocTest project

Added tests for:
- Design
- DesignSpace
Added another parameter range test

initializingParameterWithTinyRange uses the overlapSpace
design space, where D depends on A and B and will be invalid.
Merge branch 'master' into doctests
Added a test the behavior of Design.same()
Added more tests
Added type mixing tests
Added tests that examine the behavior of booleans
Added more tests

- Added cleanup to both test classes to fix a bug in the testing.
- Added a test that checks whether a design will return the same
    design space object that was used to create it.
- Added a test that investigates the relationship between design
    and design space once both have been created.
Added tests that investigate multiple ranges

- Min endpoints may never be omitted.
- Max endpoints may be omitted, but generating a value can fail.
Mostly updated javadoc comments

- Added links to related tests.
- Also tweaked the rangesWithMissingMaxFailRandomly test.
    Increased the number of generated values to increase reliability.
Added tests investigating expressions in ranges

Expressions are not evaluated for a parameter with multiple range.
References to other parameters are therefore not allowed either.
Minor comment tweaks
Added multiple tests

- Demonstrate that array elements are defined the same way as
    regular parameters (supporting expressions and multiple ranges).
- Demonstrate that expressions consisting of a single parameter
    reference cannot be evaluated.
- DesignSpace.next() can return invalid values for a parameter
    that is defined using an expression.
Added more array tests

- How does setting array elements affect arrays?
- How does setting arrays affect elements?
- Added another test of an ID containing dots.
More array tests

- How does the set of supported parameter IDs interact with array
    elements? (tested both for Design and DesignSpace)
- DesignSpace.next() does not generate array elements.
Added a nit-picky test that investigates isFile
Merge branch 'master' into doctests
Updated tests to reflect changes

The tests have been adapted to changes to the project code.
They now accurately describe what the program does.
Renamed test files to be less confusing.
Added a test for evaluation of null parameters

By creating an empty design, it's possible to force evaluation of
expressions with references to null parameters.