[MainMenu] Add clear button and icon for search one.

[Andrey2470T]

This PR allows to purge the user's search results immediately like as in the creative inventory by just pressing the new 'Clear' button. Also, this adds an icon for the current search button, instead the text. It modifies 'Online' tab and the package manager.

'Online' tab:

Package Manager:

To do

This PR is Ready for Review.

[paramat]

I assume the 'clear' and 'search' icons are taken from MTG creative mod?
If so, those textures need adding to the texture credits here

minetest/LICENSE.txt

Lines 22 to 25 in 4ba5046

	paramat:
	textures/base/pack/menu_header.png
	textures/base/pack/next_icon.png
	textures/base/pack/prev_icon.png

EDIT: Done.

[Andrey2470T]

May anybody please review quickly prior to merging? It doesn't take much time surely as this PR is
pretty minor.

[numberZero]

I’d prefer search-erase-refresh order, more like the creative inventory. Tooltips would be nice too.

[Andrey2470T]

I think the clear button yet should be first as this is common for the most of graphic interfaces. I'm unsure about tooltips, I think the icons on the buttons are already intuitively understandable what their buttons implement.

[Andrey2470T]

The PR is ready and already reviewed by one core dev. So, merge?

[Andrey2470T]

What is a current status of my PR? It is very easy and has been hanging out in an undefinitive state already two months. No feedback from the core devs up-to-day. Is it approved? If yes, may it be merged now?

[sfan5]

The broken indentation could be seen in the lua_lint run too: https://github.com/minetest/minetest/pull/10363/checks?check_run_id=1474999370#step:5:71
You didn't have to wait for me to tell you. Generally a failing build needs to be fixed before the PR can be merged at all.

[Andrey2470T]

@sfan5: I`ve fixed all what was necessary: added actual tabs in my editor and removed the whitespaces. May it be merged now?

[Andrey2470T]

Search-clear-refresh order how was requested by sfan5 on the irc:

[sfan5]

Tested.

[SmallJoker]

Works

[Andrey2470T]

Thanks. :)