Implemented Search Articles tab display order option

As per title, an option that lets you control the display order of the [Search articles] tab in the XF search area.

Core XF and Core Addons are all hard coded. The default order for AMS is 131 (most of my addons default to a value in the 100's range). If you wanted to have the [Search articles] tab before the [Search threads], you'd simply change the value from 131 to a value less than 10.

• XF: Search Everything (is the first tab), Search threads = 10, Search profile posts = 1000, Search Tags (is the last tab)
• XFMG: Search Media = 200, Search Albums = 205, Search Comments = 210
• XFRM: Search resources = 300