support lat/long in override location and avoid location lookup

[clach04]

From https://github.com/mattrossman/forecaswatch2/issues/57

Use a regex to id that latitude and longitude have been specified (rather than a place name).

E.g.:

/([-+]?[\d\.]*),([-+]?[\d\.]*)/gm

Test data set:

123.45,987.654
123.45,-987.654
-123.45,987.654
-123.45,-987.654
123.45,987.654
123.45,+987.654
+123.45,987.654
+123.45,+987.654