[css] prioritize CSS properties by usage/value

[chrisfay]

Issue Type: Bug

e.g. when I type 'back' I get background-attachment as the first suggestion instead of background. Similarly if I type 'align' I get 'align-content' over the more used 'align-items'. Atom correctly prioritizes these properties and this is my biggest complaint after switching to VCS as I'm constantly inserting the wrong properties when writing css/sass.

VS Code version: Code 1.23.1 (d0182c3, 2018-05-10T16:03:31.083Z)
OS version: Darwin x64 17.4.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz (8 x 2800)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: enabled rasterization: enabled video_decode: enabled video_encode: enabled vpx_decode: enabled webgl: enabled webgl2: enabled
Load (avg)	3, 3, 3
Memory (System)	16.00GB (0.21GB free)
Process Argv	/Applications/Visual Studio Code.app/Contents/MacOS/Electron -psn_0_3273503
Screen Reader	no
VM	0%

Extensions (12)

Extension	Author (truncated)	Version
code-settings-sync	Sha	2.9.2
jslint	ajh	1.2.1
vscode-eslint	dba	1.4.9
gitlens	eam	8.3.2
vscode-html-css	ecm	0.2.0
tslint	eg2	1.0.29
ecdc	mit	0.12.0
python	ms-	2018.4.0
debugger-for-chrome	msj	4.4.3
vscode-icons	rob	7.23.0
vscode-sass-format	sas	1.1.4
JavaScriptSnippets	xab	1.6.0

(4 theme extensions excluded)

[jrieken]

@aeschli - given equal prefix-match-scores the logic falls back to the provider sort order.

[aeschli]

duplicate of #3145