Update core.js

allow to use function as colWidths
add test for specifying colWidths as function
allow colWidths defined using primitive number or string (#947)
add tests for updateSettings
add support for column: width defined as string or number
add support for column width defined in `cells`
add support for column width defined in `cells`
Merge branch 'feature/colWidthFixes' into develop
Handsontable 0.9.15
Merge branch 'release/v0.9.15' into develop