feat(gridService): add "upsertItem" method to Grid Service

[ghiscoding]

• also rename all CRUD methods to more simple names, however we keep previous method name with a @deprecated comment.

[codecov-io]

Codecov Report

Merging #208 into master will increase coverage by 0.74%.
The diff coverage is 67.95%.

@@            Coverage Diff             @@
##           master     #208      +/-   ##
==========================================
+ Coverage   40.81%   41.55%   +0.74%     
==========================================
  Files         146      146              
  Lines        6786     6839      +53     
  Branches     2239     2262      +23     
==========================================
+ Hits         2769     2841      +72     
+ Misses       4014     3996      -18     
+ Partials        3        2       -1

Impacted Files	Coverage Δ
...modules/angular-slickgrid/services/grid.service.ts	45.53% <67.95%> (+24.81%)	⬆️
...dules/angular-slickgrid/services/filter.service.ts	17.38% <0%> (ø)	⬆️

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