Easier discovery of modern cavalry for westernized tags

[rogerburks]

References #107

The 2% discovery rate for hussars (especially) seems draconian, especially considering that it is possible in-game to discover tanks and airplanes before discovering modern cavalry. This fix addresses the problem by making the discovery rate 100% for westernized tags that have military_staff_system. This seems appropriate since hussars may have historical origins as early as the late 14th century.

The operative part of the code to fix is here, adding a 98 modifier for westernized tags:

ccHFM/ccHFM/inventions/army_inventions.txt

Lines 1202 to 1214 in e9e6e9b

	hussar_activation = {
	limit = { military_staff_system = 1 }
	chance = {
	base = 2
	modifier = {
	factor = -2
	not = { civilized = yes }
	}
	}
	effect = {
	activate_unit = hussar
	}
	}

Optionally, a there could be added a non-zero chance for non-westernized tags to discover them under certain reforms, but I have not added this.

[moretrim]

PR is good to go but I’m going to leave this open for some time. Reasons being:

• this is a gameplay change relative to upstream, so I want to mark it as experimental
• I have to go around implementing the preference system (2.0 quick list #112), to give player control over experimental features
• that control means invention chances will have to be conditional