Dppx value shown on dpi.lv is misleading when not defined in screens.json

[jjagoda]

When the dppx value is not defined in screens.json the value shown on dpi.lv is equal to 1 which is misleading.

Example:

{
"name": "Google Nexus 5",
"w": 1920,
"h": 1080,
"d": 4.95
}

and then the table "Known screens" on dpi.lv shows:

Name	Diagonal	Resolution	DPI	dppx
Google Nexus 5	4.95″	1920×1080	445	1

When dppx is unknown it should be reflected in the table as for Nexus 5 it is 3, not 1.

[CatherineLiyuankun]

Samsung Galaxy S7 dppx is 1 is not right

[arkon]

PRs for corrected dppx values would be appreciated!