Coordinates accept space separated <6 values

This PR adds back the support for space separated sky coordinate values using the sign as separator when <6 values are given. This was once supported, and I couldn't find whether it was deliberately taken out or just by accident in #2586. If the former please close the PR.
It also adds the support for the format when seconds are missing, but the minute value is a float. 
I had to make changed to the `_AngleParser` class, but left the PLY generated stuff in `angle_parsetab.py` untouched as everything seemed to be working.

The use case motivation behind this was querying a region for objects in Simbad. It give back a list with the coordinates space separated, and sometimes with less than 6 values.

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