[patch][ccla] Add the ability to style the charting grid differently from the axis ticks

[cjolif]

For now the Grid is using the Theme major/minorTick strokes to be styled.

This is a limitation because you might want totally different colors.

This patch is introducing a grid element on the Theme with major and minorLine strokes.

It also introduce on the Grid itself the same properties for both horizontal & vertical lines.

I will also attached a bit later and update of the mobileCharting demo to leverage this.

The Grid now takes uses these to draw itself. The priority is on the Grid style, then the Theme grid style and fallback to the old major & minor tick style if other properties are not set.

By default for compatibility reasons the other properties are not set.

[cjolif]

patch

[cjolif]

mobileCharting demo patch to leverage the feature

[cjolif]

See a old enhancement request about that #11389

[cjolif]

In [27000]:

Implementing grid styling by theme (overridable in grid itself). Also optionally not draw grid over axis. Fixes #13219, #13258. !strict.

[cjolif]

In [27001]:

Implementing grid styling by theme (overridable in grid itself). Also optionally not draw grid over axis. Fixes #13219, #13258. !strict.

[cjolif]

In [27002]:

leverage new grid style in demo. Refs #13219.