DOC: remove extra spaces from option descriptions 

There are already 4 spaces in the description strings in config_init.py, so no need to add some more. 
This caused the descriptions to be longer than 79 characters, and so line wrapping in the terminal. Closes #6838.

Plus, moved the default and current values to the last line of the description as proposed by @jseabold 

Example output now is:
```
display.max_colwidth : int
    The maximum width in characters of a column in the repr of
    a pandas data structure. When the column overflows, a "..."
    placeholder is embedded in the output.
    [default: 50] [currently: 50]

display.max_info_columns : int
    max_info_columns is used in DataFrame.info method to decide if
    per column information will be printed.
    [default: 100] [currently: 100]
```
Previous in 0.14 this was:
```
display.max_colwidth : [default: 50] [currently: 50]: int
        The maximum width in characters of a column in the repr of
        a pandas data structure. When the column overflows, a "..."
        placeholder is embedded in the output.

display.max_info_columns : [default: 100] [currently: 100]: int
        max_info_columns is used in DataFrame.info method to decide if
        per column information will be printed.
```
Before 0.14 it was worse (as reported in #6838), but I already improved it a bit some time ago.