Optimize tally computations (#740) ...

* Eliminate massive empty cells generation during tally evaluation

* Avoid creating cell instances when getting cell values is enough.

* Refactoring, auto format

* More tests added, functions modified

* Support tally computations with circular references

* Remove CellValues method from the interface

Fix expected order of SUMIFS parameters. Fixes #734

Fix COUNTBLANK for invalid ranges (#732) ...

* * Do not split string into chars when returning enumerator

* Fix test for CountBlank
* Simplify COUNTBLANK evaluation

* Unnecessary check removed. Code auto-formatted. Test for missing arguments added.

Correctly treat DateTime value as number in tallies.

Eliminated significant redundant iterations. (#696) ...

* Eliminated significant redundant iterations.

* Fixes in compatibility for updates to pull-request.

Fix for Issue with SumIf on "full columns" range #646 (#647) ...

* Managed SumIf on string with spaces and applied evaluation of values only when condition is satisfied (resolve "recursion" problem due to use SumIf formula in same range for values).

* Sample application for issue tracking

* Developed requested changes for pull request #647

* Removed sample project in wrong place

* Required changes

* Merge reset

* Removed undesired blank line

* Removed tab

SUMPRODUCT: Blank cells and cells with text should be treated as zeros

Merge pull request #586 from igitur/ExcelNumberFormat ...

Use ExcelNumberFormat library to format strings.

Use ExcelNumberFormat library for Text() function too

improve FACTDOUBLE and add unit tests ...

FACTDOUBLE now throws correct exceptions and

improve Fact (throw correct exceptions on invalid input), add unit tests

improve COMBIN and add unit tests ...

COMBIN did not handle non-numeric values correctly. Should throw NumberException (#NUM in Excel). Returned 0 for any non-numeric parameter instead before

implement BASE and corresponding unit tests

throw correct exceptions on ATANH and add unit tests

fix ATAN2 implementation and add tests ...

Math.Atan2() expects y as first parameter and x as second, while in Excel x is first,
throw "correct" exception on input (0, 0)

add unit tests

improve ASIN: throw NumberException for values not in range for Excel ...

...add unit tests for ASIN

implement ARABIC and unit tests

restrict valid input range to [1..) as in Excel, add unit tests.

fix ACOS implementation: in Excel only defined in range [-1, 1] ...

if input is not in range, throw exception.

adding unit tests for ACOS

fix C# version compatibility issue - thanks for the hint ;)

implement SECH function and corresponding tests

implement SEC and corresponding unit tests

implement ACOTH function and corresponding unit tests

implement ACOT function and unit tests

implement CSC function and tests

implement Coth and tests

Feature/sumifs and countifs (#561) ...

* implement SumIfs and some tests

* implement CountIfs and some unit tests

Merge pull request #555 from jongleur1983/548-conditionsForStrings2 ...

#548 enhance string condition capabilities of CalcEngine

Allow Hyperlink to have 1 to 2 parameters

#548: test empty string condition for countIf, & corresponding fix