add dialog to export and import settings text files

[commy2]

When merged this pull request will:

• fixes a bug where settings are not displayed correctly in ui after #"import"
• copyFrom/ToClipboard has stupid limitations in MP, so let the user press Ctrl+C/V on a edit box instead

It scrolls for more than 40 settings and can display thousands.

[Dorbedo]

I think, it would be an advantage, if the settings would be exported sorted by category. Maybe even with a comment.

// category 1
setting_category1_A = 1;
force setting_category1_B = 2;
// category 2
setting_category2_A = ABC;

I recognized this feature as missing while exporting the ace-settings

[Dystopian]

it would be cool if only changed settings could be exported

[commy2]

^ fixes https://www.youtube.com/watch?v=F-whgpGviRU&feature=youtu.be

[commy2]

Done and done.

[Dystopian]

add _skipDefault to header?

[Dystopian]

Tested, works great.
If have few non-default settings and uncheck Show default values, comments are really superfluous. It would be good to have checkbox to disable comments (and maybe double newline between categories).

[commy2]

I think the comments are great and a checkbox just to disable them feels like "too much".