bwg improvements

+ added pythonic command existence checking.
+ split clipboard copying to its own method.
+ bwg accepts "full" to copy all login fields.
- disabled addins for the time being.
+ improve installation instructions.

.gitconfig

@@ -13,5 +13,6 @@
 [core]
 	editor = vim
 	autocrlf = input
+	pager = less -x1,5
 [commit]
 	gpgsign = true