fix(formatters): decimalSeparator & thousandSeparator work tgt, fix #411

[ghiscoding]

• when using both together, 1 was cancelling the other. To fix this, I rewrote the code use text split by the decimal and then recombining them as a new text with necessary thousand & decimal separators

• fix code

• add unit tests to cover both properties used at the same time

with updated code, the result is now as shown below

1. first column has thousandSeparator: '.' and decimalSeparator: ','
2. second column has thousandSeparator: ',' and decimalSeparator: '.'

[codecov]

Codecov Report

Merging #415 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #415    +/-   ##
======================================
  Coverage     100%   100%            
======================================
  Files         141    141            
  Lines        8857   8863     +6     
  Branches     3055   2931   -124     
======================================
+ Hits         8857   8863     +6

Impacted Files	Coverage Δ
...pp/modules/angular-slickgrid/services/utilities.ts	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 72870f4...af146fb. Read the comment docs.