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:

cc @eteq, @taldcroft
```
In [2]: astropy.__version__
Out[2]: u'1.0.dev9597'

In [3]: from astroquery.simbad import Simbad
WARNING: ConfigurationDefaultMissingWarning: Could not determine version of package astroquery Cannot install default profile. If you are importing from source, this is expected. [astroquery._astropy_init]
WARNING: AstropyDeprecationWarning: ConfigurationItem has been deprecated in astropy 0.4. Use ConfigItem objects as members of ConfigNamespace subclasses instead.  See ConfigNamespace for an example. [astropy.config.configuration]

In [4]: import astropy.units as u

In [5]: obj_list = Simbad.query_region(coordinates='08:51:18 +11 48 00')
WARNING: AstropyDeprecationWarning: The format function is deprecated and may be removed in a future version.
        Use to_string instead. [astropy.utils.misc]
WARNING: AstropyDeprecationWarning: The format function is deprecated and may be removed in a future version.
        Use to_string instead. [astropy.utils.misc]

In [6]: ra=obj_list['RA']

In [7]: dec=obj_list['DEC']

In [8]: from astropy.coordinates import *

In [9]:  Angle(dec, unit=u.deg).deg
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-9-de86a4894c9b> in <module>()
----> 1 Angle(dec, unit=u.deg).deg

/Users/bsipocz/munka/devel/astropy/astropy/coordinates/angles.py in __new__(cls, angle, unit, dtype, copy)
    116                   not (isinstance(angle, np.ndarray) and
    117                        angle.dtype.kind not in 'SUVO')):
--> 118                 angle = [Angle(x, unit) for x in angle]
    119                 if unit is None:
    120                     unit = angle[0].unit

/Users/bsipocz/munka/devel/astropy/astropy/coordinates/angles.py in __new__(cls, angle, unit, dtype, copy)
    107 
    108             if isinstance(angle, six.string_types):
--> 109                 angle, new_unit = util.parse_angle(angle, unit)
    110                 if new_unit is not None and unit is None:
    111                     unit = new_unit

/Users/bsipocz/munka/devel/astropy/astropy/coordinates/angle_utilities.py in parse_angle(angle, unit, debug)
    345         string.
    346     """
--> 347     return _AngleParser().parse(angle, unit, debug=debug)
    348 
    349 

/Users/bsipocz/munka/devel/astropy/astropy/coordinates/angle_utilities.py in parse(self, angle, unit, debug)
    261             else:
    262                 raise ValueError(
--> 263                     "Syntax error parsing angle {0!r}".format(angle))
    264 
    265         if unit is None and found_unit is None:

ValueError: Syntax error parsing angle '+11 48.0'
```
```
In [15]: print obj_list[0:3]
        MAIN_ID               RA           DEC      RA_PREC ... COO_ERR_ANGLE COO_QUAL COO_WAVELENGTH     COO_BIBCODE    
                           "h:m:s"       "d:m:s"            ...      deg                                                 
----------------------- ------------- ------------- ------- ... ------------- -------- -------------- -------------------
                  M  67      08 51 18      +11 48.0       4 ...             0        E                2005ApJ...619..824X
2MASS J08511918+1147546 08 51 19.1817 +11 47 54.708       8 ...            90        B              O 2006A&A...448.1235D
          ** BPM  480BE   08 51 19.19   +11 47 54.8       6 ...             0        D              O 2001AJ....122.3466M

```
Maybe this should be a compiled regex at the module-level (``PMRE = re.compile((\+|\-)')`` at the top, and then call with ``coord = PMRE.split(coord)). That will be faster, and when parsing long lists of string coordinates, this code is repeated many times.