fix($location): don't initialize hash url unnecessarily

After a recent refactoring using $location in the default hashbang mode would result
in hash url being initialized unnecessarily in cases when the base url didn't end
with a slash.

for example http://localhost:8000/temp.html would get rewritten as
http://location:8000/temp.html#/temp.html by error.
chore($location): drop bugus error

we can never get to this state, so dropping the error
docs(minErr): add location/ihshprfx
docs(minErr): add location/isrcharg docs
docs(minErr): add location/ipthprfx