[0.15.9] Lua API doc mistakes

[daniel34]

Trying to change the technology price multiplier using Lua I found the following:

• technology_price_multiplier can be read/written using DifficultySettings, this is missing from the documentation.
• Accessing game.map_settings.difficulty_settings.xyz doesn't work (unknown path difficulty_settings) although difficulty_settings is defined in the map-settings.lua. This should be clarified in the documentation or map-settings.lua file, or access to it should be allowed.

Second issue:

• The help function (Common.html#Common.help) is listed in a lot of classes throughout the API and is always declared as read-only string property although it is in fact a function that returns a string.

[Rseding91]

Thanks for the report. I've fixed the first 2 things - difficulty_settings has to be changed through game.difficulty_settings due to how it changes the game massively when altered - which is why it's not available in map_settings.

[Rseding91]

The help function is also now fixed for 0.15.10.