counsel-rg gets no search results on Windows and result links can't be followed

[mwolson]

The default value of counsel-rg-base-command is currently missing the . parameter - without this, rg version 0.3.1 will fail to find any results on Windows.

Further, it is also missing --line-numbers which is necessary to follow links correctly, and there are multiple problems with the C-c C-o command.

An incoming merge request will address all of this.